The TTS synth is a very nice synth and has multi-channel capability, and yeah, I've heard some amazing musical projects from people who used it to do an orchestral project that was jaw dropping. And as I recall, the person in question claimed to have moused every note for every instrument into the midi tracks.... making it even more impressive.
However, I have stopped using it for the most part since it is a basic synth and uses patches vs the better synths which, now days, use samples. It has a purpose and a place, to be sure, but sound wise.... there are a bunch of synths on the market and in my VST list that sound better.
I use the Cakewalk Sound Center synth now for several things since it is a sampled synth. In addition, I have a number of other synths, including Kontakt, which support some amazing samples and of course, Kontakt has one of the larger third party supplied sample libraries around. Both of these, however, are one channel synths so to do 4 instruments requires 4 instances of those synths in question. Not really a major issue, since freezing the synth or render to audio removes all of the processing..... and you have a simple audio track to work with.