He has more than four amps.winisd is a program that should help you greatly, and if you want to do 4 z1s and 4 btl 18s fully loaded then your a rich mofo an your being very similar to steve meade who runs 4 btl 18s and 4 fosgate 4000watt amps in a tahoe. batteries and alts wont be cheap at all. but nice idea. If I was in your shoes I would keep the kickers and make them work, cause that will get stupid loud either way you look at it, and less power overall LESS money.