What is poering your subs now? Your amp should be powering your subs, not your radio. If you are not getting any power from the amp in one car, but you are in the other, then I would check all my stteings on the amp to make everything is set perfectly. I got sony amps powering the main speakers in car, but my subs sounded weak until I got a seperate eq to balance out my system the way I wanted it to sound. You also might want to check your amp fuse that goes to your battery (you might have blown it in one car and not the other). YOu might want to get a Cap, I got a 2 farad cap and my needle still dips to the red at full blast.