mleghorn
As for sound quality of the digital out of my sound card: it's perfect -- nothing can top it. For what it's worth, it's Realtek HD, and it supports up to 192000 Hz / 24-bit. My audio system downstream of the digital out (Burson Audio Conductor, HD800, Cardas Clear cable) gives the whole picture. If the sound isn't perfect, I hear it :-)

Yes, I was referring to the analog out of your sound card, so of course you'd want to use the digital out. As long as there's no significant jitter one digital out should be as good as any other.

The Focusrite Scarlett 6i6 has what you are after. And the drivers are proven to work by 100's of Sonar X3 users. 
Tascam seems to be still struggling with drivers. I have the Tascam us1641 and it works OK, but just OK. I had a huge jump in performance when I bought the 6i6. I keep the Tascam for when I need 16 channels. 
 
I guess Bob and I were right about asio4all  after4all, I to give them credit for creating a free software that does work really well for a lot of audio applications. It's just never  worked with Sonar as far as I can tell from dozens and dozens of threads here over the years. The phrases Sound Blaster and Asio4all will always raise a red flag. 

johnnyV
Tascam seems to be still struggling with drivers. 

Well, I've been beating up the new drivers for the US-4x4 pretty heavily...if nothing else they're certainly much better than the ones in the V-Studio. I agree that previous generations of TASCAM drivers were problematic, but apparently TASCAM thought so too as they're now doing drivers in-house. And of course, TASCAM tests the drivers extensively with SONAR. Granted the interfaces are quite new, but at least here, it's so far so good.

I've started using the Tascam US-366 interface. I've uninstalled ASIO4ALL. I have a project I've been working on that has 8 instrument tracks with Dune 2. I have three busses with Valhalla Room reverb, and sends from the 8 instrument tracks to the three busses.
 
I went away on vacation for a few days, came back, and the project is hosed. When I try to play it, there is a loud click, and all meters on all the busses show red.
 
Can I send Cakewalk this project so they can figure out the problem?
 
Thanks,
Mike

I'd advise calling tech support first. I'd be willing to bet that your project will play back just fine on most systems where basic issues have been addressed to improve performance with real-time streaming audio. A loud click and all meters showing red is almost certainly a hardware problem; if not, it's a plug-in problem. I don't believe Dune 2 and the Valhalla reverb are unusually CPU intensive, but virtual instruments push a computer much harder than audio tracks.
 
 
Try opening SONAR and putting in something like six instances of Rapture, six instances of Dimension Pro, and a few Breverb reverbs. What happens?
 
Also there are a variety of issues with laptops that work against performance:
 

• Wi-fi and network adapters need to be off
• Power-saving features need to be turned off because they throttle back the CPU
• The power plan should set the CPU to 100%
• Drivers loaded for functions you don't need, like the drivers to transfer audio to televisions, can impact performance to a huge degree

 
Have you tried running at the longest possible latency to see if things work? Then you can work backward from there. 
 
There are programs like LatencyMon that can show exactly what's going on insider your computer that 's taking up power. There may be startup programs you don't need or drivers for peripherals that are irrelevant but are loaded anyway.
 
Your project is almost certainly not what what's being hosed, unless it's having problems with a particular plug-in; your computer is likely what's being hosed, so fixing the problem requires finding out what's going on with your system. Tech support can walk you through some things to consider. There are also a ton of threads in this forum where people have had similar problems and fixes were arrived at eventually - use google to do a site search on latency, Latency monitor, and wi-fi...see what shows up.

johnnyV
The Focusrite Scarlett 6i6 has what you are after. And the drivers are proven to work by 100's of Sonar X3 users. 
Tascam seems to be still struggling with drivers. I have the Tascam us1641 and it works OK, but just OK. I had a huge jump in performance when I bought the 6i6. I keep the Tascam for when I need 16 channels. 
 
I guess Bob and I were right about asio4all  after4all, I to give them credit for creating a free software that does work really well for a lot of audio applications. It's just never  worked with Sonar as far as I can tell from dozens and dozens of threads here over the years. The phrases Sound Blaster and Asio4all will always raise a red flag. 

Well, in actuality, ASIO4ALL has worked for some folks running Sonar - but it does cause problems on an awful lot of systems, and the conclusion I have reached in my head is that it is not worth the headaches and heartaches.
 
If someone wants to invest time money and effort into using Sonar, then they should if at all possible find a way to buy a dedicated audio interface.  
 
A decent audio interface can be purchased for as little as $150, with 2 ins and 2 outs, decent mic pre-amps and converters, midi ports, phantom power, and drivers through Windows 8 and 8-1.
 
Bob Bone

Thanks to everyone for all of your input on this issue -- Thanks Craig for making me suspicious of other devices and drivers that might not being playing well.
 
I believe I've found the culprit: my M-Audio Keystation 49 keyboard. I'm able to start up all of the supposedly hosed projects as long as I don't have the keyboard plugged in.
 
Go figure. This is all the more reason I need to find a MIDI interface that works with my system. I've ordered the EMU MIDI / USB cable. I've got my fingers crossed.
 
On another note (pun intended), the Tascam US-366 exceeds my expectations. Not only does it work fine with X3, it's an improvement over my on-board sound card. When listening to music on my sound system, which uses the optical out from the sound card or US-366, I'm noticing more detail, space, and dynamics in the recordings. This is huge to me. Best $200 I've ever spent!
 
Thanks,
Mike

I spoke too soon. Problem came back, even after no longer having the M-Audio keyboard plugged in.

Just in case - it might be worth running Regedit and doing a 'Find' for the string ASIO4ALL, in case the uninstall didn't delete all the pieces.
 
I dimly recall at least one occasion in the past where an older release of it had left some things behind - believe it was in the current user keys, but if you click on Computer (high-level node in registry hive navigation tree) and then do the find it will search the whole registry for any occurrences of that string.
 
Bob Bone
 

Please also list the following information:
 
1. What is the Sonar Driver Mode? (Preferences>Audio>Playback and Recording)
2. What are the Sonar-reported latency values? (Preferences>Audio>Driver Settings)
3. What is your ASIO Buffer Size set to for your audio interface?
4. What happens if you temporarily Bypass All Effects by hitting the letter 'E' on your computer keyboard, and then hit Play? (I didn't find info yet on web about the potential for latency issues from that Valhalla Room plugin, so you can test that out by doing the Bypass All Effects thing with hitting 'E'.  Hitting 'E' again after seeing what happens in Playback will turn your effects back on, by the way).
 
Bob Bone