its a ****ing nova man, for one you cant **** up a nova. i don't give a shit what you do to it, have vagrants piss on it ill still drive the mother ****er. and how is spl a bad set up, those things are solid steal a sq set up is just as worthless. its not like having this set up will kill his car. but to get back onto your point yes i think a 18 is a tight squeeze, id say get some L7 but that is just because I'm a fan of there subs. id just get two of them tho and i think you will be happy they ask for min of 2 cubes each and a max of 3.5 so i would really only get two, and kicker has a nice amp to go with them i think its a 1500 watt at one ohm load, so with two duel 4ohm dvc 12's you will give them there exact rating(however alot of people say they will take 1k rms all day long)personally id swing away from kicker amps tho, have one and i love it but it was 2nd hand(cant see paying sticker price for one) id look up sundown as mentioned up top(not the cheapest but great ****ing amps) or hifonics(what I'm using not the best but **** cheap). well i think that is about both ends of it and ether way you go you are looking at under 1000, but you must remember your yellow top and big three you will need after all that. oh ya and your new tweets and amp or you will hear nothing but bass!!