Mine sounds best in my building's old-school wooden elevator, but I find it hard to book rehearsal times!
I've got a cheap Chinese instrument that I picked up for about R3600 with a bow, case, stand and rosin.
If you DO buy a cheap Chinese bass I recommend getting the bridge reworked, the fingerboard redone, buying a new set of strings and getting it set up by a professional.
Fishman also make a pretty reliable Piezo pickup for Double Basses that just clip neatly on top the bridge. For a more realistic sound for quieter settings, I've also seen guys mount a condenser mic under the bridge between the posts.
If you want to play Rockabilly, get Weedwackers (
http://www.gotofmi.com/upbaclkerowe.html). They're made of nylon and definitely give you a more authentic tone, not to mention the fact that they're very easy to slap. You will naturally lose warmth of tone and sustain if you use nylon strings tho.
If you're based in Cape Town, phone Sergio at 021 558 2524 for any and all your upright bass needs. He's the MAN when it comes to this stuff.