just got that sony head unit that you can download your music onto the faceplate,now im looking for door speakers and rear deck speakers ,I dont really know that much about car audio ,i have a 12" infinity sub ,Well my question is will the head unit be good enough to run the 4 door speakers and what size speakers do you guys suggest, i know the stock size is 6x8 but can you put 6.5 or 5 1/4 in there. Also i have a 4 channel amp can i run the sub and the deck speakers off that and use the head unit to run all the door speakers.Sorry if i sound dumb but ive never really learned much about car audio.And i have the alpine system. thanks