first of all you don't buy a higher capacity alternator, you simply have your stock one respooled. this can take a 60amp alt up to about 100amp if required. this said unless you plan to run 10 amps your stock alt will work fine. if you kown anything about audio there are little things called capacitors which store power for peak usage of your subs that will work the trick under most circumstances. saves getting your stock alternator respooled. go here for an explanation and a price - http://jaycar.com.au/productView.asp?ID=RU6752&keywords=capacitor+car&form=KEYWORD Welcome to TOC!