I've got a 2001 with the bose system still on my car, i've also got a jl 500/1 amp with 2 12" w3's on my car and the polk audio ex3500 tweeters, i want to know if i can change out the remainin 4 speakers and put a 4 channel amp and still have the factory headunit on the car? ..... i dont have the cash to get the headunit i want but i do for the speakers and amp.