| Never been much of a fan of that overly bright sound me-self. I usually play passive J-basses these days and I especially like it when the strings get old and gross. While some may suggest flats, they just weird me out - gotta have those roundwounds under my fingers.
I had a basic Corvette (passive, bubinga, etc.) a while back and also had a Bartolini system from another project sitting around which included a bass/treble preamp and pickups that were either 9J1's or 9J4's - sorry, but it was a while ago. With those electronics in that bass, I thought that I had a "buttah" factory on my hands and if I wanted to get a little slap happy, I could just tweak the high end freq's on the bass and have a Marcus/TM Stevens sort of moment. Then I played out with it a couple of times and found out what the downside of a super smooth tone can mean. Despite my competent rig, my sound with that bass just didn't cut, especially with a pair of guitars to compete with.
Around that same time period, I had also acquired a 2nd hand Jazz that I decided to try a set of DiMarzio Ultra Jazz p/u's with and while the Bart's in the Corvette may have been great if I needed a really slick sound in a studio bass, the rumors about the DiMarzio UJ's proved to be true. This bass is my bold tone machine, even with the passive tone knob rolled most of the way back to keep the bright stuff under control. I avoided trying the Bart's in a passive set up because a big write up at the time noted that they had a noticeably low output - one more thing you may want to check on before you get a set. I'm looking forward to trying a set of DiMarzio's Model J's when I can given my experience with their stuff so far.
I hope that this hindsight might be helpful even though it's not a story about another Thumb being converted to a passive set up. | 
