I am going to gut my 2002 out and replace the entire system. I have Kenwood Excelon speakers for the front and rear and want to have a sub in the back. The headunit is an Alpine CDA 7998 w/no power. In speaking to an installer he suggested an Alpine 5 channel amp to power all the speakers. The price isnt a big deal (500 at tweeter, 300 online) but I want to know if the 5 channel is what I need for all four speakers and the sub or can I go with something else, like a 4/3/2? Any help would be appreciated.