The Z5500 Logitech speakers are an amazing set of speakers. Make sure you get the NEW VERSION of the speakers. The old ones had the crappier colored speaker plugs, whereas the newest set has the normal speaker wire, that you crimp in. Makes it so you can put in like any other speakers as well, or upgrade the length of the speaker cable with ease. You can get them for super cheap compared to similar systems from creative etc. If you dont want to spend as much, the z5300e are also a very very good set of speakers (what i have, I was very impressed. It makes it sound like you are actually in a tank in BF2). Anyways, maybe check out
www.logitech.com for more info on the speakers.
-Ian