I've used the RBI loads and its my favourite tone with a fender jazz and sounds great with a Status Stealth that my friend uses. I guess that extra knob would give you a load more range, but the only thing that would worry me its not soley designed for bass so maybe its a jack of all trades but master of none?
In saying that though back in the early 2000s my old band did a tour with a UK band called One Minute Silence and their bassist was running the PSA into some warwick stuff, and that was brutal. I guess it would be worth having a browse on the Basstalk forum see if anyone is running one.