I had that I bought a 50W for the fronts and that's when the noise problems started. I first checked to see if it was power-signal wire interferences-Nope. Then wondered if the fact the signal wires went close to the car computer was it-Nope. I proceeded to Radio Shack and purchased a Ground Loop Isolator (Cat. No. 270-054) that plugs between the Empeg's RCA outputs to the Amp's inputs and no noise problems anymore.

Radio Shack also had a similiar Isolator that hooked between the car battery and power wires to the Amps but I didn't try them after success with the aforementioned.

#090000695 Mk2 BLUE 12Gig