People in hell want ice water, but they aren't going to get it either. $500 might be a minimum target price for a very basic 3.1 system that sounds halfway decent, but $250 sure isn't.
I would advise you to get a pair of Polk Monitor 40 speakers, which Amazon has for about $160 per pair, and then save up for a Polk PSW505 subwoofer for around $250. The Monitor 40s are fairly good speakers that have some bass.
Than you can save up for a CS20 center speaker and you will have a decent basic 3.1 system for around $600.
Another possibility is the Jamo S426HCS3 system, which will give you 5 fairly decent speakers for around $250 or so, and then add the PSW505 later. That Jamo setup is exceptionally good for such a low price, and the speakers have a bit of bass. That is probably your best bet.
None of that fits my definition of decent sound, but you would need $2000 or so to go there. It's a modest start, anyway.
Edited by commsysman - 7/11/12 at 4:21pm