help...looking for the right subs for my set up

[reddtheLegend]

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.

[mylows10]

the american bass vfl 8 should work nice for your app,150 shipped new from me

[reddtheLegend]

those are some hefty subs, my initial plan was to run both subs with one of my old school mtx 2600rt. will these be happy with 300 watts each @ 2 ohms? i have two of the rt2600's but i'm not trying to rip out my 4awg to run 0awg because i'm lazy.
what is the mounting depth?
the wife has limited me to $200 so i'm gonna have to make some concessions in order to spend the extra.