wait does this exist? I was thinking one day. Feeding a power amp with my laptop where I am selecting from at least 20 heads, 20 cabs, how ever many effects I want and to what degree I'd like. Also having a tuner in it and sheet music. I guess I have way too much time to think
Well it does exist, kinda.....
As BFBT suggested earlier in the post, IK Multimedia's suite of plugins give plenty of options in the amp, cab, mic, effects, and routing categories. I currently use IK's Ampeg SVX, Fender, and Amplitube 2 with X-gear. X-gear is great because it provides a single interface for any IK package you have. They also include a tuner and trainer w/looping functionality. I can combine signals from guitar AND bass amps/cabs/effects and create very unique hybrid tones for my bass (or guitar).
I haven't used NI's Guitar Rig, but I hear it is an excellent software package, more geared towards guitarists though, not bass players.