I have a four channel amp and I am running the dash and door speakers on the "front" two channels. All the speakers are coaxial. Obviously I am running the rear shelf speakers on the "rear" two channels. I have gotten mixed opinions on this. My head unit's built in crossover lets me manage Front, Rear and Sub hence why I didn't look for a six channel amp. I wasn't sure how I could have managed the crossovers via the head unit. All this being said, is my set up acceptable?