Too many adapters... :)

How long is the interconnect from your empeg to your Sony? Mine's only about 4" (ya, inches) long. Do you hear the noise on all your speakers, in-car-only or sub-only? I find it strange that the ones off your Sony head have noise. I would definitely use a shorter/better cable between the empeg and Sony. And again, try a different ground spot for the Sony and the Empeg (ground them to the SAME spot). Normally people will pick up noise in a run of cable that goes from the front to the back of the car.

Bruno