I have the same problem, but I'm under windows 7 with different rig. (Sorry for borrowing your topic, but since the problem is the same I figured why the hell not)

Asus P8Z68 DELUXE/GEN3 as a motherboard
Intel i5 3570K as a CPU
nVidia GTX 680 as a GPU
Steelseries Siberia V2 Frost Blue edition (USB) (it has it's own audio card, so I'm using it).
HDMI and every other possible sound income has been disabled other than the steelseries one and I've tried drivers dating months back with no result.
Only thing that seems to help is to turn up the volume on the headset and lowering it from windows to balance it out (then again, it gets fecked at times even at highest possible setting when it tears my brain apart).
Any of the suggestions given here didn't help in the situation.