I am running a 3.5mm to RCA adapter from my on board audio to RCA's into my head unit and I really couldn't be happier with the sound. I know that my setup is not the same as yours, but I would try running straight out of your MB with an RCA adapter and see if that helps. And I am using a crappy wal mart brand 3.5mm to rca adapter that I had at home until i can get a better one. My experience with cables is better cables=better sound, but better cables don't fix problems. Hope this helps and keep us posted.