Ok I just bought the logitech z640s and hooked them up and i'm not getting sound out of the two rear speakers. So far I have tried mp3's with matrix on and off and unreal tournament 2004. Anyone know what the problem could be. Also what sounds better, the computer volume low and using the speaker volume control or putting the speaker volume on say 5 and using the computer volume? And I'm just curious... whats the average volume you guys have your sub set at?