If your only getting a single AQ 2200, why spend the extra money to get two subs. Just get one AQ HDC3 and be happy. It'll take up less space, and you save 300$. Just my opinion. What vehicle btw?
Edit: Orrr, why don't you take the money you save from not getting either AQ and buy you something nice, like a Lv 5 or the like. It'll sound alot better on the power, and you can get another AQ 2200 for it down the road.