In response to the OP. The TTS1 soft synth is a GM2 compatible soft synth and if I'm not mistaken uses the Roland GM2 sound set (the GM2 sounds they shipped with their hardware synths).
That being said, the GM2 sound set is woefully lacking for modern production or 'pro' sound. I don't think that was the designers intent in the first place, the sound set was originally intended as a standard for hardware vendors to enable the same MIDI file to sound similar on any synthesizer. When the standard was created, there was no such thing as a DAW or soft synths for that matter, MIDI files were created and used in sequencer programs and if you wanted other people to be able to play your composition you had to stick with the standard.
In response to the notion that things should sound perfect in your mix using stock patches, it simply doesn't work that way. Music production is hard work and sometimes it takes a while to get the sound you're looking for. Cakewalk makes a couple good multi-sample synths (D-Pro, Rapture, Rapture Pro), well one synth in various flavors anyway...
and an analogish synth (Z3TA) but even if you're a preset producer you'll still need to tweak the patches to fit your composition.
Bottom line, no soft synth is going to give you exactly what you want without tweaking, that's just not how pro works. That's not Cakewalks fault.