power cap or bigger alternator

hey. I have a 95 ex coupe. My system has an alpine amp to run some beasty type r subs, but i'm stuck on the power issue. My alternator only puts out 30 amps and that is max at 3000 rpm's.

Should I get a power cap to keep my electrical system from getting drained (about $150-200), or get a 70 amp alternator for $120 from pep boys. I know i probably will want a power cap later on anyway, but, im debating on whether or not I need a bigger alternator. The amp can draw about 25-30 amps continuous if cranked up and max out at about 55 amps, so i know i need to do something about the power.... alot of people though just run a power cap with a huge system and no alternator upgrade.

Just wanted everyones input on this before I buy the alternator.