Ok.. here is the problem
I installed My Fosgate 200M amp for my SUb.. install went fine.. we got power and everything

When we connect the RCA cable input (from the rear speakers) the audio from the radio turns off (but the radio is on), when we pull the RCA input from the amp, the sound for the door speakers and rear speakers come back on. Also, if we left the RCA input plugged into the amp and disconnected the negative from the amp, the door and rear speakers come alive again. Any Ideas??