I REALLY like K&K pups on my ABG, and so does everyone else

I bought a Michael Kelly Club Deluxe 5-string ABG on ebay, and really took to it, but it had that clacky cheap-piezo-under-the-bridge sound. I had luthier Karl Hoyt (you should check out his basses, btw) install a K&K pickup under the top. It was compatible with the onboard pre-amp, which made for an easier installation.

This made such a huge difference in the sound, which was pretty good already. If you're thinking about upgrading your ABG -- or getting one and upgrading it -- I highly recommend doing so. It didn't change the looks of the bass at all, and it's a far better instrument for it.
 
Oh cool. I'll look into this. I'm quite happy with the pickup now (an artec undersaddle) but a second voice might be cool.

FWIW, the tone of a (regular under-saddle) piezo pickup depends greatly on the preamp in the bass. More specifically, the input impedance of the preamp. The cort has a Fishman pre, and it's fine, but other AGBs I've worked on have had way too low input z and I've even modded one or two with a fet input buffer. This hugely improved the tone of these basses.

Here's a video with some of the set up jobs I did on my ABG.

And if you skip to 8:30 in this video, you'll see what I mean about the input z.