Here is something for you.. the JBL P1224 or P1222
They are monsters, youll need a custom box though for them as they are slightly larger than your typical 12" but its worth it.. If your looking for SQ, then go with a sealed box, not only will you have better SQ than a ported box, but also will sound better than a ported on a wider freq range.. Ported only sound good around the small band of the box's tuned freq.. the rest sound like farts.. Dont be fooled by the RMS rating, they are under rated, every install of one of these are running around 800RMS and they can take the power.. One in a 1.4 Sealed will sound like 2 12's in the trunk all by it self..
I used to run one of these in a 1.4 sealed box, only pushing 480 RMS to it.. and it was plenty enough.. then upgraded to a JBL 1200.1 II-Z amp pushing 800, it was insaine, then i upgraded to 2 of these subs, now they are really insane..
Here is a link you you can at least take a look if you want..
http://www.crutchfield.com/p_109P1224/JBL-P1224.html?search=JBL+VENDORID109&ssi=0&searchdisplay=JBL
$199 here, and you can find cheaper around some other net sites,
ebay you can get them refurbished for maybee 1 bill.