I don't have a drop-in, but I've put Audere 4-band Z-mode module preamps into two basses and still own one of them. It's a parts bass Jazz that I put Nordstrand NJ5S pickups into. I find it very neutral and very flexible.
The luthier who assembled the bass for is the one who suggested the Audere to me. At the time, I had heard of them but didn't know much about them. Glad he suggested it, this bass looks pretty bad (an SX Jazz body with horribly matched pieces of wood in the body) but it sounds fantastic. My band loves it, especially our gear head guitarist, who prefers it over my L-2500 and Stingrays.
EDIT: I also requested a change made to the knob configuration on the preamp in my parts Jazz. The standard config of the four knobs is volume, balance, treble over bass, and hi mids over low mids. I figured I'd probably want easier access to the two mids knobs than bass and treble, so I had them change the tone knobs to hi mids over treble and low mids over bass. That ended up working our real well. I like that config a lot.