Have you tried to make the repair yourself? Might be super easy and save you some money.
I did replace the amp that I received from Axiom to repair the Sub. The problem actually started when I replaced this. I can shake the cable in the back of the sub and hear it cut out.
Actually I think I'd lay money down that the replacement sub does the same thing ... i.e. you said it happens when it's off. Sounds very ground loopy to me ...
This happened in my old house before I moved too. I am going to try a Klipsch from Costco and see if I can replicate it.
