Last night, I pulled out my old Squier P-bass 5-string for a full setup (including a fret scrub - I hadn't really touched it in six or eight years and the frets were actually visibly rusted) and a fresh set of Elixirs. It was a cheap bass when I bought it, I think I payed $2-250 new, but after I set it up and got new strings on it I was actually really impressed by just how good it sounded. It had a nice, thick, punchy low B, and pretty good balance between the B and the higher strings.
I was never happy with the tone from it back in the day, but in retrospect I think that was likely due to 1.) poor technique 2.) poor signal chain (a Johnson J-Station SVT model direct into my laptop's line in - an input that was in particular hard on the low end) and 3.) my habit of just rolling the tone knob all the way off.
I was setting it up to loan to a friend who wanted to try playing bass, but after messing with it a bit I think I may actually miss it a little after I give it to her.
New strings on any bass make a monster difference too.