You need a bigger amp and make sure its a two channel. Four and five channel amps are for mids and highs. If you want real bass get a two channel. If you dont want to buy a bigger amp, Go get a capacitor. It acts like a battery charge storage for when your sub needs to hit those real low notes. It takes a lot of power. Also if you get a capacitor your altinater that charges your battery will not have to work so hard keeping your battery charged, Thus not wearing out your altinater and not having to replace it so soon because it will happen.

Another quick fix is turning your gain down. I turn my gain up half way, maybe a little past half way. You might not get the bass hitting as hard but at least it wont shut off on you.