without someone who knows what they are looking at actually having it and taking it apart then we PROBABLY can't help you honestly. I know there are a few amp fixers on here that you may be able to send pics to but that seems pretty far fetched.
you could also have something silly going on like a grounded speaker wire (spade terminal touching the metal of the door) try just hooking it up with some speakers in the trunk or wherever on a cardboard box 1 channel at a time to see if it's all toast or the problem is only 1 of the channels.