Are you only interested in being loud or do you want something with good sound quality? What, if any, equipment do you already have? If the $2000 has to buy a head unit, component speakers, subs, amps, wiring, and deadening, you're options start to get a bit limited. You can still do a lot with two grand, but you have to do a little more bargain shopping.
There is a lot more to a system than subs and an amp. If you get too big of a substage, you won't be able to hear the music, and you'll have to buy a whole new front stage anyway. Best to think about that now before you spend all your money on the loudest subs you can squeeze in.
Also, with such limited space, I'd suggest just getting one really good sub. That way, you don't have to work so hard to squeeze it in, and more money can be spent on other components of the system. One good sub should get more than loud enough to fill a camaro.