Hi there, i would go with what the boys are saying, i built an install for my estate a few years ago running 2 amps together 3000w, 4x150w 6x9's and a550w audiobahn sub with a neon light ring and 2 blue led computer fans to aid cooling of the amps, at first i had everything running off the standard alternator and the car battery, however the sound when cranked up left a lot to be desired, after looking through forums i stumbled accross
www.the12v.com,the amount of info on this site is astounding to say the least and i soon had my alternator upgraded and was running a second gel type battery in the boot, i would also have installed a power cap but didn't have the funds to do so at the time. hope this helps !!