i want to get a second battery for my suburban. i have a sears plat. as my main battery and a dc 270 as my alt. i am running 4 kenwood amps. 2 xr1s running at 2 ohms for 700 watts each and 2 xr4s running 300 x 2 at 4 ohms. i also have 6 7" screens and 2 22 screens and a xbox 360. i want to be able to run my system at shows while the engine is not running. whats the smallest battery i can run? the space i want to run it in is small. but if not i will get a regular size battery but i want a small battery. thanks in advance.