there are several people that can design boxes on here, prices from 10- 50 bucks or so.
also I like my aq2200 amp. contrary to popular belief you do not need to over power those subs to get them loud. my amp is only at 2 ohms right now, so my subs are only seeing 5-600 each or so (not quite at rated) and they are loud. I will eventually get 2 more 12's and run them on the 2200. after that i will upgrade to the 3500.
I wouldn't buy a cheap amp or multiple amps. start off with a good 2000 watt amp. then upgrade later. or if you have the cash now buy a 3500 watt amp now.