Ok so I've got an Ibanez BTB 5 string from 8 or 9 years ago (before they switched to basswood and all that). A buddy of mine suggests going with an Aguilar Premp - OBP3.
I brought that sucker home last night and holy crap - what a world of difference. Really added that missing piece to the btb. Recommend it to anyone looking for an 18V preamp.