Check to see if it's wired correctly. Contact kicker, they'll be able to help you better than any of us here. And consult your user manual. The troubleshooting section works wonders when something does wrong. But if it's going into protection when it turns on, generally means that it's wired...
Take your car to a place like AutoZone or Advanced Auto parts. Typically, on the top of the battery, it should give you some information about it. Like, total voltage..etc. Optima is a good battery. Sears and Costco might be able to help you, but I'd stick with AutoZone or Advanced Auto...