I have almost no experience with Peavey's bass gear, but I've played with a number of people who use Peavey guitar amps like the XXX, Valveking, and Delta Blues and they always had some pretty great tones going. I'd imagine it's the same with their bass gear: the budget end stuff will be passable in the tone department and the higher end offerings will be better. You just don't see as much of the higher end Peavey stuff.I can attest to Peavey's reliability, I put my old TKO through a window and still used it for practice that night.
However, I have yet to hear a tone I would consider anything better than adequate from a Peavey.