Keegan only mentioned 1 place that I would buy anything from and that is online car stereo. Crutchfield will only rip you off. I will give you a link to buy some subs that will blow away those MTX subs that your thinking of buying, I personally would not buy anything with MTX name on it, I put them right there with Sony. There is also www.woofersetc.com
But here is the link I was talking about:
http://www.edesignaudio.com/index.php?cPath=1_21