Shifting Problem

I just put a new 1000 watt system in my grand am, it is hooked directly to the battery through a capacitor. I am starting to get real crappy shifting and I think it is because of the power the amp is taking from the battery. The amp is sucking up so much juice that the car has minimal power. I would just like to know if I am right befor I blow $150 on a Optima battery. Oh yeah I have the crappy stock ac delco battery. E-mail me back at [email protected] and let me know your take on it.

Thanks