I have dual batteries on my boat. My Head unit plays when pergo switch is on battery 1, 2, or dual batteries. My question is if I hook up an amp, which battery do I hook power and ground to from amp, or does it matter? Just want to avoid having head unit on and amp off, and vice versa. Want to make sure they will both be on at same time. I'm not sure which battery HU is hooked to now. I am assuming it doesn't matter, if whatever switch position you have it on, the head unit plays. Any help is greatly appreciated.