I'm gonna go with the setup i have in the first post and get this sub in the future (a while):

Which would you recommend?

Kenwood KFC-W112SKenwood KFC-W112S (KFCW112S) 12" KFC Car Subwoofer

Pioneer TS-W309D4
Pioneer TS-W309D4 (TSW309D4) 12" Dual 4 Ohm Champion Subwoofer

or any other you suggest