Reply to Studio Wiring Assistance

So I've recently purchased a pair or Gold KRK 5s (from guitar center for a wicked price of 110 dollars with their up coming January clearance: AKA Check that out lol) and upon setting them up, I noticed a low pitched hum that seemed to sync up with what my mouse was hovering over on screen. Different Icons had slightly different frequencies.
So I've separated my computer from the outlet the monitors run from.
Made sure all the outlets were properly grounded.
Separated most cables behind the computer.
Funny enough it seemed the main problem was a thin USB wire running from my computer to my sound card was crossed with my computer power line. Changing the cable ultimately reduced the hum to almost inaudible. However whenever my mouse runs over any icon on screen, I still can hear a quick buzz from my monitors.

I was wondering if the USB cable in the DJTT store would fix that completely?
And is there much else I can do to keep any garbage noise out of my monitors?