I have a project which i'm sure some people have completed. I have a wagon that i plan to design and build a box for to contain 1 12" kicker comp, 2 6.5" coaxial speakers and a head unit. The sub woofer is powered by a 300.2 kicker amp and the coaxial speakers are going to be powered by an offbrand 240 watt 2 channel amp. My question is what amp per hour battery should i look into buying? I plan to roll these speakers on the beach maybe going half volume. I want it to be able to last at least around 4 hours without draining. I was also thinking about getting 2 batteries and wiring them to double the life. Any suggestions?