Good that you could solve your friends problem too.

I also had this issue. Luckily for me my cable and electric service come into the house at the same point. I was simply able to take the main cable coming in and use a cable grounding block to ground it to the main ground for the house. Problem solved.

BTW, your setup looks great with the M22's on the Velo subs.

Dan
On-Wall M5HP LCR, QS8 & EP500 in 7.1