It looks like (from your first four posts) you are doing a pretty good job figuring this out on your own. TTS-1 is a Swiss army knife as far as synths go (multitimbral). You can run 16 tracks (or keyboards) into it, each patched to a different instrument, and send the output to eight different output tracks. It has a really low demand on your system and operates with minimal latency. Wonderful tool to use while tracking.
When you insert TTS-1 use the "All synth audio output" option and you can send your bass to a separate output audio channel which you can then distort to your hearts content without affecting the other instruments.
I would suggest however, that you try a different approach of adding a synth instance for each MIDI track and use a few of the far better synths that come with X3. Try inserting "dimension pro" and redirecting the MIDI track output to it. There are tons of exceptional bass patches (programs) that you can load into dim pro that will knock your socks off. Then, if you still need it, add distortion FX to the dim pro track. If TTS-1 is a Swiss Army Knife, Dim Pro is a Samurai Sword. It can only handle one thing at a time, but it really handles it.
Session Drummer 3 rocks for percussion.
Glen