I have the Polk Audio DB212-2 set up in my car. It has two 12's and a ported whole.

db212-2 Car Subwoofer from Polk Audio

Dimensions: 16-1/4" H x 34-1/8" W x 17-1/8"

It fits pretty good in the back, I can take it in and out whenever I feel like it. Also you still have some room for stuff if you want in the trunk