I have recently bought a car with an aftermarket system. Nothing major. The front two speakers are stock but there is a new head unit and a new pair of 6"x9" in the rear. Everytime i run the radio over 20 or so volume, the stereo cuts out. I was wondering if that has to be a problem with the wattage of the head unit. The head unit is 45wX4 channels and the 6"x9"s are 220 Max watts each, (440 Watts). Do i need a new head unit? if so what wattage do i need?