As Felix stated, we need to know what sort of soundcard/on board sound you have, plus it would also help to know what sort of quality you are going for...
Most new motherboards these days have decent onboard optical audio out or multiple 3.5mm ports for decent surround sound. Or even as Felix said, some have RCA out.
Creative and Logitech have some really nice sound systems from a huge range of prices and features, but they are aimed at computer audio (Games, small room sound sort of thing)
I have a
Logitech Z-5500 for my general gaming and computer/console stuff.
I also have my larger Sony surround system for the loud stuff which is also connected through optical audio and is quite good.
So yeah, tell us what your after and i'm sure there are heaps of people here that can give their opinions and advise [img]smile.gif[/img]