Esh, it is good to see you and others well ahead of me in the use of software/hardware based solutions. You certainly have an interesting and good looking system....no doubt about that!!!
I too as you know have Colossus but can't get the GM/program change mode to work well with kontakt. However, once that is accomplished and you use DFD (disk streaming) with a fast hard drive the loading time will become less of an issue. I am still working on this as well. If the sound quality is good in Bandstand then Bandstand will be the answer for GM (Auto Accompaniment & midi). In addition, if you can change out any of the instruments you do not like with better ones then Bandstand will be worth its weight in gold (not much weight...).
Again, it is good to see some of you taking the software (or software & hardware) route for your arranger and performance systems. I am in deed becoming to frail to make much of a difference anymore and look forward to your leadership and advice.
Have a good musical journey....