99,
I would have the two amplifier grounds connected to the same point. Unless of course they are half a cars lenth apart from eachother, umm maybe they are though. When making grounds, make sure the metal is not painted or sand of some paint to get a bare metal connection. also go for a thick pice of metal on the body of the car, somewhere on a lap joint or reenforced area.
try this, it is good practice anyway.
later,
chris
