I want to coax my buddy into upgrading the stereo on his boat he just got. I don't know if it has any changes to the factory set up yet, but he is into nice systems so i wanted to get some advice. i'll figure out what tower he has and all that when i see the boat. I want to say a pair of 485's with a syn-4, a XXX with a syn-1, and wire the bow speakers into the factory clarion amp with the other two pair of in boats. and a 420 as well. Where is the best place for a 3rd battery, how would you place the sub? in a box under the passenger seat or is there a better place for it?