i have a 2006 pontiac gto and have been trying to figure out a subwoofer setup. for those who don't know there's virtually no trunk space because the gas tank is in there. this makes putting an enclosure back there a no go since it's my dd. i've decided to replace the factory 6.5" subs with 8" subs in the rear deck. this is a somewhat common thing among gto owners but i can't get much help there with sub selection. since the set up is free air/infinite baffle there aren't many subs to choose from. i'm not exactly sure what specs to look for in a sub that will work in this application but these are some that i have looked at thus far:
Polk Audio db840
Precision Power PPI A.8SQ
MB Quart RLP204
i've also considered the image dynamics 8 but i'm looking for dual 4 ohm.