Wanted to get a new head unit/stereo/cd player whatever you want to call it that'll directly input to my ipod. On the cructhfield website, it says you have to but an aftermarket amp and a low pass crossover if I want to keep my factory subs when I added my head unit to the cart. Would it be cheaper just to buy $130 aftermarket subs to put in the trunk to avoid buying the crossover and amp? It ends up costing about $100 for the crossover plus another 100 for the wiring kit and then 30 for the crossover. Could you buy the subwoofer without the crossover and amp or would you need them anyways? I wanted to spend no more than 350 on everything....is this possible?