i have a logitech z-5500 and it is simply amazing.. louder than you could possibly need.
My only complaints are the inputs are one optical, one digi coax, and the 3 mini plugs that make up surround sound, i wish it had a simple rca in. Also the sub is very loud and great for explosions while watching movies (great example in hollow man 2) but it sounds kind of sloppy sometimes when listening to music (still would give it a 8/10). My last complaint is my first sub blew, but then again i was intoxicated and playing it at like complete full volume.
if you can cough up $260ish you can find it on buy.com with free shipping (thats how i got it) and its worth the extra money