I read a thread somewhere (not on this forum) where somebody didn't think that Peavey's preamps were high end or detailed compared to other well-known names. I think it's a classic case of "what does the headstock" say syndrome. I've played US Barts and found some examples to be rather dark and almost muddy. Although I have a bass that has EMG's, I've played examples that were sterile and ice picky.
I've also seen examples where people will change pickups without giving the stock set a chance at all. Looking at the circuit boards and layout it's apparent that Peavey when through painstaking lengths to get their stuff tight. I wouldn't be surprised if the owner that changed the Mill's electronics to Barts did so to make a double profit since the preamps are so sought after.
I played my GV at rehearsal last Friday and was very happy with the results. Very comfortable to play and very natural feeling. I paired with my EBS T90 and a single Baer 12. Good stuff!