any good free air subwoofers?

hi, i was looking at getting subs for my car and i was thinking of getting a free air set up so that i would still make use of my trunk and i was wondering if there is anygood free air subwoofers i would prefer a 12 inch but will settle for 10 inch. brand i really don't care to much and price it can't be more then 750.

Image Dynamics, check em out.