Simple wins the day in my opinion. 
 
Get a good USB connected interface that runs native ASIO and be done with problems. 
 
They sell the USB cord gizmo's because there's a bunch of poor musicians who can't afford to spring for a decent interface.  $20 vs $200.  And for the most part, they kinda work some of the time. Enough for the companies to keep making and selling them. Of course, they have lots of drawbacks.

Would this setup let me record multiple midi tracks, each having different instruments before reconfiguring for audio conversion? And would it let me select Ketron instruments/patches from Cake?
 

oh yeah, absolutely.  just record the midi to separate MIDI tracks in MC, then wwhen you set up to record the audio from the Ketron, just set each MIDI track to a different MIDI channel.
 
it will all come out still on just a stereo audio track that way, tho. in order to have individual instruments on their own track, you'd need to record the audio one (or two at a time because the behringer will only record main outs, so set one to the left and one to the right and record separate audio tracks for each input at a time from MC.
 
But I'd also recommend replacing that Behringer USB cable converter with a decent soundcard/interface to get low latency
 
http://www.musiciansfriend.com/pro-audio/focusrite-scarlett-2i2-usb-audio-interface
http://www.musiciansfriend.com/pro-audio/roland-ua-22-duo-capture-ex-usb-audio-midi-interface
http://www.musiciansfriend.com/pro-audio/roland-quad-capture-usb-2.0-audio-interface
http://www.musiciansfriend.com/pro-audio/motu-microbook-ii-audio-interface
http://www.musiciansfriend.com/pro-audio/focusrite-scarlett-6i6-audio-interface
http://www.musiciansfriend.com/pro-audio/presonus-audiobox-44vsl-usb-2.0-recording-system
 

Spending a few hundred more isn't an issue for me - ignorance is the killer. Since midi was invented I've been creating sequences - hundreds of them for gigs and classrooms - starting with Sequential Circuits, Korg Poly 800, Roland D-20, Roland XP-50, and Cakewalk. I didn't have to understand much except what I liked to hear. Now I don't even know what "USB connected interface that runs native ASIO or USB cord gizmo's even refers to or why I would need to know, let alone how to connect them to one another and set the preferences. MIDI-based recording, it seems, has become something like a basket of green parts dumped in front of a medieval peat digger who is told, "These will connect to make a John Deere backhoe." But step by step, I'll get there. Thanks for your guidance, guys.

Since you have the money..... get an interface today.
 
I use Focusrite. I like them because they have nice audio preamps for those times when you need to record with a condenser mic. (Which is always)
 
Connect the interface to the computer..... set it up with ASIO drivers. 
Connect your monitor speakers to the interface's audio output.
Connect your midi keyboard to the interface MIDI IN. 
Connect audio stuff... mics and guitars and even the keyboard audio out if you like how it sounds
.....and you're all set to go.
 
Start Music Creator and it should see the new interface in both the midi and audio in/out.  Select and set the interface as the default if the computer is a dedicated DAW.....and you're ready to start recording and capturing the midi. At this point, MIDI/synth playback and monitoring should be essentially, latency free. Life will be good.
 
In my system, and it's an older system now, (i5 chip on XP32) the only latency that I can hear, and it's barely perceptible, is when I'm attempting to run a guitar amp sim plugin. Since I don't like the way they sound, and prefer to mic a real amp or use my POD2, that's really not a problem. My synths otherwise are running around 5ms which is imperceptible to my ears.
 
I don't even know what "USB connected interface that runs native ASIO or USB cord gizmo's even refers to or why I would need to know, let alone how to connect them to one another and set the preferences.
 
so... let me explain it a bit:
 
USB connected interface.... simply any external third party soundcard that is connected to the computer via a USB cable
 
native ASIO.... the ASIO drivers for audio use. Many of the inferior sound cards and cheap interfaces do not run on native or "real" ASIO.... instead, the manufacturers rely on a wrapper like ASIO4ALL to make a less capable driver such as MME, appear to be ASIO to the hardware. Some manufacturers also use their own software called CODECS to make their cards work. Neither of those are as good as native ASIO.  Sure they work in most cases but can often be problematic when they are pushed to and beyond their limits with  large audio/midi projects and lots of plugs and synths.... ASIO will generally be able to keep everything running and the only limit is the computer itself.
 
cord gizmos:  usb style cord devices that are designed to let you plug in a guitar or mic to a usb port. The UNO is one of those. They do not have the hardware, ports in and out for audio and the software to do the job properly and efficiently. I tell people to avoid those things like the plague.  Save the money and get a decent interface.
 
As I pointed out in the first part of this post...connecting a decent interface is a breeze.  If I recall, my default settings on the Focusrite interface I have worked perfectly. I didn't need to make ANY adjustments to get flawless recording and playback with non-perceptible latency.
 
With my Focusrite.... since the interface has pristine, crystal clear audio preamps, I do not even have a mixer board in my studio let alone connected to the recording path.  Mic/guitar into the interface, into the computer, into Sonar... done.
 

 
 
 

I may soon order a Focusrite. However, the scene is evolving here with endless puzzles. By starting with no template on MC, then inserting a couple of midi tracks, suddenly latency is gone. Next problem is: I can make no sense of how to assign patches to the tracks. In the Inspector pane, I select a Ketron patch for track 1, record it, and all goes well. Then for track 2, I select a different patch and all goes well - if you ignore that you have to stop/start the track once to get the instrument to switch. Each recorded track plays its respective patch, but when both play together, they divert to the patch of track 1. I've tried setting channel 1 to track 1, and 2 to 2, but when I do that, track 2 has no sound.
 
In 1989 I turned on the Roland D-20 and within 5 minutes was laying down multi-track recordings. Guys, we're going backwards at the speed of light. Any suggestions for giving this junk I have a fair test? I can't help thinking it'll fly once I figure how to tell track 2 I want a trumpet with no argument. How hard do they need to make it?

My web site has some very basic info on how to assign patches using TTS as the synth. 
 
http://www.herbhartley.com/hh2_edited_slimmer_005.htm   scroll down to ADVANCED TTS SETUP.....   and follow the instructions step by step. Substitute your sound card/interface in place of mine where I have "FR" in the process. I recall having to do the start stop thing you mentioned. However, once you understand how to properly assign the patches, you won't have to do that.   I remember everything being "properly assigned"... or so I thought, only to hit play and have all the tracks sound like a piano. Be sure you place the patch assignment in the  proper place in the midi track and not in the synth channel.  You must set the channel correctly and the patch, both in the MC midi track. If you only set the patch and not the channel, the data from that track goes to the channel you didn't assign, which ends up being the default of 1 or 0..... whichever, which is piano by default, and that's why you hear all the tracks playing as the same instrument. You have to change that channel assignment. That tells the midi track in your project, which channel in the TTS synth to send the data to.

I believe that's correct since it's literally been 4 or 5 years since I have used TTS.
 
I do not use any external synths. All my synths are software based. AKA: Softsynths.  Everything I do is "inside the box" as they say.
 
I don't use templates.  I open a new project and select "normal" from the list for type. It gives me a basic 2 track starting point. I delete the midi track and add more tracks as I need them. If I am planning on using a softsynth in the project, I will add that manually when I need it. By choosing INSERT SOFTSYNTH, I only have to select the synth I want to use. Sonar makes the internal connections automatically and all I have to do is assign the patch or sample I wish to have the synth use. Each synth varies in how this is done. Once you do it once or twice it becomes second nature.
 
You also need to understand if the synth you're using is mono channel or multi channel..... in other words, can the synth play multiple instrument tracks and have each one play a unique instrument voice or does it only do one voice for each instance of the synth in the project.

TTS is multi channel in that one instance of TTS will allow you to assign 16 individual midi tracks to it's channels and each one plays a different instrument. That's what I have on my web site. I show how that's done.
 
Calkwalk Sound Center synth is a mono channel synth. Each instance supports one track and one sample for that track. If you want a different sound with the first one... you have to add a second instance of the CSC and assign it a different sample.  Most of the higher quality synths are mono channel.  In fact, I think TTS is the only one of the dozens of synths I have, that does support more than one channel at a time. 

Having a good sound card/ interface will not hurt when it comes to working with synths. Get that Focusrite and get it working..... don't give up.   It took me several weeks to get a grasp on this process just to get sound..... and now it's all second nature to set up new projects and do what needs to be done.  It might seem to be a harder path than you're used to but it's really not. It's just that you have to learn some new things. I would not want to go back to what seemed easier at the time..... nope, this DAW I have now is so much better and more capable of creating music and recording.......I love this thing.