Radio/tape Cd Player problems of the 2009 Mitsubishi Lancer

I have an 09 Mitsubishi Lancer ES sport with the sun and sound package. The amplifier, which is under my drivers side seat, for the sound system started smoking and sparking. I took it to the dealership, who replaced it, and a week ago, while I was driving, it started smoking and sparking again, but stops when you power off the radio, if the power is on in the radio, it continues to smoke and spark. I believe there may be a wiring defect in my car that is causing this to happen and fear that if it continues my car may eventually catch on fire. Dealer will not look at it again unless I pay $120 initial fee.