alright - here's the deal - more or less killed my battery with my sound sytem

I need a double battery unit, I know ( I have two amps, a 10in sub, and 4 6X9s running off of an 875 battery - that runs my car too )

anyways. So I buy a new battery. I turn off my kill switch for the system, install the new battery, turn the switch back on, put a cd in my headunt, turn up the volume... nothing. Look in my trunk. Amps aren't even lit up!!!

And as far as I'm aware, only two fuses are there, and they're up front. The car came with this system already, so I'm clueless :confused: any help would be mucho appreciated ( especially hands on )