Well, this weekend I had the opportunity to replace my pickups in my MIM 50's P bass. First, I'm in love with my T-bird and this one just sat around most of the time and doesn't get a lot of attention. Don't get me wrong: love the action and the feel of the neck but the stock MIM tone just sucks! My guitar tech kept telling me the MIM PU are as good as the MIA's so I never bothered upgrading them. I just chalked it up to not buying a MIA and agreed to suffer with an inferior Fender product, hence - no love! After reading a recent post regarding Pups someone mentioned Bartolini's as "dark witchcraft"! That's all I needed to hear! Bought a set of 8CBP (apparently the darkest of the dark) from Catalina Guitars out of AZ for a very reasonable price. The interesting thing is my tech had a set of SD 1/4#ers that he wanted me to try as well (these WERE my first choice). Besides a lot of soldering and de-soldering, set up and tear down we got through it. Didn't get to record any of the variations but to cut this short: the MIM pups got tossed. Disclaimer: If you have the original MIM Pups in your p-bass - get rid of them - the difference between these and either the SDs or Bartolini's (probably any pup for that matter) are an upgrade you'll never second guess. We installed the SDs first since I was set on the Barts. The SD's were such an improvement over the MIMs that I thought why go any further. The tone was bright, rich and mellow! The bass finally came alive! However, once I got the Barts installed and started playing I was in another world. To be honest, the difference between the 1/4pdrs and the 8CBP is hugh. The Barts bring a deep rich low tone that neither the MIMs or 1/4pdrs come close to. What was even more impressive with the 8CBP is the clarity and sustain of each note is incredible. I could go on and on. Funny thing is I played the p-bass all weekend and into the week. I just can't believe how bad the original tone was with the MIM pups. A final note - I don't see why you'd need to add a pre to the Barts. As passive pups they deliver and deliver strong high end gain. They're hot!