Randy,
I had ground loop hum issues and the only thing that would fix it was running a wire between chasis of receiver, ground screw on sub, chasis screws on any/all other equipment. This wire just needs to be small 18 guage. I guess this equilized all grounds. All I know is it made my system dead silent and did not hurt bass output. I had made up some test wires with gator clips to find problem. All of this equipment was powered from same circuit through a surge protector.