I have my stock AM radio in the dash. I have an amp in the trunk that powers my speakers (kick panel and back seat panels, plus a pair of 4.5 inch full range under the dash on the tunnel in a custom enclosure). My trick is that the amp is fed audio signal via a bluetooth receiver which in turn gets music from my iPhone or my iPod classic. Therefore, I have a cordless system that is theft resistant since I remove the "head unit" each time I leave the car.