I actually have the Logitech 930's and though I am not the one to go to for sound quality (ears arent that good) they sound good enough for me. The issues I have are:
1- the 7.1 is nothing like real 7.1 thru speakers, making the tracking (front/rear) difficult for me (remember I dont have great tonal hearing)
2 - the usb interface drives me nuts. I cant unplug them and have the system switch over to my speakers automatically. You have to shutfown the game/program/video you are one and manually switch to your soundcard and the start back up whatever you were doing. I have 100w speakers for a reason! LoL
My suggestion would be to get a good quality pair (or better if your hearing is better then mine) of standard stereo 3.5mm headphones...