Besides Cakewalk TTS-1 are there any other synths that will allow me to assign different patches on each of the 16 MIDI channels? I'm guessing that would be less CPU intensive than having 16 different synths playing. The GM parts of TTS-1 are OK for some things, but not nearly like the high-dollar samples we purchase. Any thoughts?
 
Thanks

There are some older ones, I think.  Like the Roland Groove synth.  But as you've noticed, Cake has gone for quality over quantity, despite Lenin's axiom.  Dimpro will do 4 midi channels, but I think multiple instances will all start on midi channel 1.

Hi EFaaT,
 
FWIW Rapture can also do Multi-timbral.  So you've got up to 6 parts per instance.  Just make sure for each instance of Rapture you assign your MIDI tracks to MIDI Channels 1-6 respectively. 
 
Looking at your computer specs they seem pretty decent.  Are you having performance issues running multiple VSTs?  It seems as though your i7 and generous RAM amounts should chew through multiple plugins and instruments quite easily.

IIRC, IK Multimedia's Sampletank (latest is Sampletank 3) is also multi-timbral. EastWest Quantum Leap (EWQL) Symphonic Orchestra, among others, is also multi-timbral. But of course, both of these virtual instruments are outside of what comes with Sonar.

Kontakt here, though I don't think there's anything else quite so convenient as the tts

In addition to sampletank and eastwest, and i would place UVI works station in that group, there is the multi-tuimbral sampler route like Kontakt. I can't think of any that are cheap though, however once you own, there are many free sounds for kontakt. Sampletank may be the cheapest route to get reasonably full set of instruments. Definitely major upgrade over tts-1.