Earlier I mentioned running a hifi rig like a Contra, or a Clarus with outboard speakers (my rig) and using a Bass Pod to add harmonics and distorion for BG. I just noticed that Musicians Friend is blowing out the Korg Toneworks modules for $49 (guitar) and $59 (bass). That bass unit would be a good (and cheap) way to add amp and cabinet non-linearities to an Acoustic Image rig so you could use it for UB, EUB and BG.