On ebay, put in the search "chevy high output alternator 160" and ull see CHEVY C K GMC TRUCK HIGH OUTPUT NEW ALTERNATOR 160 AMP. i called the dude(company) up and they said they have a 160 amp for my corsica for 110 shiped... thats not bad right?.. let me know, cause im plannin on gettin it... cause i just have stock 105 right now so maybe im only getting 700-800 rms right now??
Sean brings up a good point. Make sure the idle isn't to low. What does your system consist of? 160 might be enough for you. But if your thinking about upgrading down the line might get something bigger.