I'll probably go the route that Frank went and get a high quality set of GM samples and / or a higher end soft GM modules in the near future.
Until then, I am rather satisfied when using the SGM180 soundfont with a touch of additional reverb and chorus effect mixed in. I have some higher quality effects packages, yet in this setup, I find that the freeware "Classic" Series Chorus and Reverb plugins do a very nice job of enhancing SGM180.
For the first time since I've owned it ( several years ), I actually like using Band in a Box. It sounds very nice now when I use it with Live Synth Pro and SGM180 and the effects setup I described. In reality, to my ears it is a step up soundwise from Hypercanvas. SGM180 also does a very nice job with OMB and Chainer as my Vst host, particularly when I use non Yamaha kb styles like those from the KN7k and Roland series boards. Again good but subtle ( ie. not overdone ) effects added make a world of difference to me.
I actually think this setup in itself now exceeds anything soundwise that my PA80 can do for me. That's before I add the high quality softsynths that I already have for lead voices. I can only imagine what a higher quality GM set would do for me for the rythyms and styles.
Actually, I have made a few rythym setups up for Chainer, that include Yamaha Blue Jay drums, the B4 organ, assorted basses ( sampled ), and ElectroAcoustic and / or Real Guitar for guitar rythyms. Incredible sounding at times, even with BIAB.