A few weeks back, I encountered an issue with no sound in my Sonar X3 template. This seems to have been relieved. Here's a summary of the progress involved, as discussed in this Forum thread.
 
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EARLY MAY: ISSUE
Sonar template created and saved with 12 tracks and no data. No sound heard from drum tracks.
--- Later noticed no sound from all synth tracks (rather than just drum tracks).
Sound would return upon insert of new track.

5/12: FOLLOW-UP
A fellow Forum user tested the template; confirmed audio was heard.
Believed the cause was no instruments set on some tracks, but still no audio heard.

5/15: OBSERVATION #1 & FURTHER ISSUE
Idenitified that the Audio Engine button was disabled on startup.
Through moderate experimentation, noticed Audio Engine disabling at "random" times.
Upon reporting, was strongly recommended upgrade to an audio interface.

5/18: OBSERVATION #2 & FOLLOW-UP
Tested all of my current projects in progress; all played back fine.
Created new template; issue still persists (no sound on any track).
Via further experimentation, identified the Audio Engine doesn't enable without data to play.
--- After draw of first note, Audio Engine enables and track plays back fine.

SOURCES REVIEWED
Cakewalk Documentation: The Audio Engine Button
--- First paragraph: "When playback is in progress, Audio Engine starts automatically"
Cakewalk Forum thread: "Audio Engine Won't Start"
--- Post #2: "Audio engine won't start without data to play"
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SUMMARY
It was suggested that this issue wasn't worth researching without an audio interface, but I was compelled to continue in the meantime. I was relieved to notice that the Audio Engine truly won't trigger on without data to playback -- a complete oversight of logic and common sense.

I'm in no way negating the need for an audio interface. I'm just merely noting that, hence the previous paragraph, I seem to have identified/resolved the problem -- at least part of it, or the blatantly obvious. :)

REMAINING QUESTIONS
How is it that the Audio Engine button doesn't trigger until the track is played?
Shouldn't I be able to insert a synth track and hear the notes outright when sampling them from the corresponding Mixer window? I swore I was able to do this in MC6 without having to play a track to enable the sound.

AUDIO INTERFACE
Over the past few days, I have researched different devices, two of which are available at my local Best Buy. They are by M-Audio and Focusrite, per this link.
 
Can anyone offer any opinions on these? The reviews look pretty promising. In the meantime, I feel a renewed sense of confidence and I'm going to continue working as usual.

Thanks to all who participated and I look forward to further suggestions on anything mentioned here.

OK - a couple of thoughts on the interfaces you are looking at:
 
1.  IF you need midi ports on whatever interface you pick up, neither one of those 2 interfaces has them, so you would not be able to connect anything through a midi connection to your computer.  This is normally only an issue if you have older external keyboards or rack-mounted gear, or perhaps a midi foot controller for guitar (Behringer FCB1010 comes to mind).
 
2.  Of the 2 interfaces you are looking at, I believe the Focusrite will have the better sounding preamps, from reports I have seen.  
 
3.  They both seem to have Windows 8 drivers.
 
Here is a link to a post I made earlier today for someone else who is looking at interfaces:
 
 
http://forum.cakewalk.com/FindPost/3040835
 
Guitar Center has a really nice one with midi ports and Windows 8 support, and is a smaller version of the audio interface I happen to use.  So, take a look at the above post - it's $119.99 new.
 
Bob Bone
 

My shopping list: 

I needed a min of 6 inputs and 6 outputs.: 
      2 Combi front panel inputs for instruments or Mikes. 
      2 line level inputs for Analog mixer. 
      SPDIF input for Digital Mixer ( = 2) 
MIDI input for Controller
4 analog outputs must be balanced for FOH patching. 
SPDIF output 
MIDI output for hardware synths.
2 Headphones with front panel control
Front panel Monitor level control. 
Pre Amps must be regarded as good quality by reviews.
Phantom Power
Front panel Computer/Input Balance control
Input Metering 
NOT MADE OF PLASTIC! 
Small and portable
On /Off switch
A/C powered
 
http://www.gearslutz.com/board/reviews/906141-focusrite-scarlett-6i6.html
 
 

I wouldn't worry about the audio engine button. Once you have a solid audio interface it wont be an issue. 
 
I just opened an empty project. No audio or MIDI in it. The button was grayed out showing that the audio engine was not running. This is to be expected. The way CW has programed Sonar is the button is there so we users when we run into trouble we can manually turn off audio to prevent unpleasant sounds from hurting our ears or speakers. Its a convenience not some diagnostic tool. 
 
As one presenter pointed out many years ago at a Cubase demonstration outside of video processing multi track audio is the most demanding form of computing a user is likely to deal with. I don't know how true that statement was but no matter, it is a real burden on a computer's CPU. In order to have a well functioning system for multi track audio we need to enlist a quality audio interface to take some of the burden off the CPU. This is where it is fundamental to get a good interface. Its drivers will allow the software to access the DSP of the device in real time and with low CPU. This is not true for a multimedia audio chip on the motherboard. 
 
Because we have CPUs of enormous power in comparison to the past it would seem that it shouldn't be a problem anymore for a low end chip to rely on the CPU for many of its processing needs. That is true in many cases. Except that multi track audio with a lot of native plugins engaged and virtual synths and samplers demanding the attention of the CPU and a further demand that the audio be instant with no latency it is no wonder that quality audio interfaces are used by the great majority of DAW users. They promise low latency and multiple audio streams with no unnecessary demands made on the CPU.  Audio engines will run and processing will happen happily.
 
If you were to take a look at just what goes on internally with Sonar's audio engine when you press play you would be bewildered and bewitched and beguiled by all that is going on. It only stands for you to provide an environment that will help not hinder all the bits going hither and yon.             

John
I wouldn't worry about the audio engine button. Once you have a solid audio interface it wont be an issue. 
 
I just opened an empty project. No audio or MIDI in it. The button was grayed out showing that the audio engine was not running. This is to be expected. The way CW has programed Sonar is the button is there so we users when we run into trouble we can manually turn off audio to prevent unpleasant sounds from hurting our ears or speakers. Its a convenience not some diagnostic tool. 

Thanks for the explanation; I'm beginning to understand this better.
 
However -- can you answer me this: Why is it that, when I create an empty project and insert a synth track (i.e. Sound Center), I go into the library, select an instrument and 1) it does not sound, 2) but the sound returns (as well as audio engine comes on) when I insert another synth track?
 
I swear I don't remember it working like this, at least, until not with Music Creator and not long after I installed Sonar. I'm just curious, as I used to be able to sample the instrument library outright without worrying whether the audio engine was on.

Creating an empty project should have the audio engine enabled, at least this is the case with my interface. Don't know why it is not consistently happening when using the internal sound chip. Maybe windows sounds or another app are interfering with it.
 
One thing about being a SONAR owner is you are entitled to free phone support. Tech support may be in a better position to offer an explanation.
 

Grundberg

John
I wouldn't worry about the audio engine button. Once you have a solid audio interface it wont be an issue. 
 
I just opened an empty project. No audio or MIDI in it. The button was grayed out showing that the audio engine was not running. This is to be expected. The way CW has programed Sonar is the button is there so we users when we run into trouble we can manually turn off audio to prevent unpleasant sounds from hurting our ears or speakers. Its a convenience not some diagnostic tool. 

Thanks for the explanation; I'm beginning to understand this better.
 
However -- can you answer me this: Why is it that, when I create an empty project and insert a synth track (i.e. Sound Center), I go into the library, select an instrument and 1) it does not sound, 2) but the sound returns (as well as audio engine comes on) when I insert another synth track?
 
I swear I don't remember it working like this, at least, until not with Music Creator and not long after I installed Sonar. I'm just curious, as I used to be able to sample the instrument library outright without worrying whether the audio engine was on.

I don't know except I avoid Sound Center. I used it once just to see how it works and if I could get any use out of it. Sadly my impression was its meant to highlight sound packs from CW for other synths. In other words its a promotional tool not a useful synth. I had glitches with also. 
 
What I use is Kontakt 5, Dimension Pro GPO, BFD3 and a whole lot of other synths. I do not use Sound Center.  
 

scook
Creating an empty project should have the audio engine enabled, at least this is the case with my interface. Don't know why it is not consistently happening when using the internal sound chip. Maybe windows sounds or another app are interfering with it.
 
One thing about being a SONAR owner is you are entitled to free phone support. Tech support may be in a better position to offer an explanation.
 

I think you created it and this may be the reason. I opened one that has no audio or MIDI in it. 

IDK, I have an empty project (I believe you do too). When I open my empty-x3.cwp, the audio engine is enabled. The only thing in empty-x3.cwp are the default Normal.cwt buses and a limiter in the master FX bin.

Here is the empty project. The audio engine is off.