[aunchaki]

I like GK solid state amps and cabs for bass. Their Backline series of cabs come in every flavor (2x10, 4x10, 1x15, probably others). My last band had a few of each that we mixed and matched and combined.

I'd give the stock bridge and pickups a chance before swapping them. Even as I give this advice, I know that I've ignored it myself. Often.

I like heavier strings on a 4-string because I like to play in drop-D. It depends on your own style. I put flatwounds on my old P-bass, before I re-gifted it. My current bass is a J-configured 5-string and I'm still using roundwounds (that's MY preference: flats for Ps, rounds for Js). I don't have much string brand wisdom; I've used Fender strings without complaint. My next set may be Ernie Balls (if they have what i need). I don't change bass strings that often.

Basic set-up issues are not that much different from a Strat or Tele.

Good luck! Welcome to the basement!