I've got a Carvin LB70P on the way to me. I've heard that the build quality is excellent, but the electronics/pickups are pretty average. Eventually I'd like to replace both the pre and the pups, but I can't afford to do both at the same time. If I were going to replace the pickups or the preamp which would be best? I'm sure that a Bartolini NTMB preamp would work, but the Carvin also has a piezo bridge - how would I replace the Carvin pre with the NTMB?