My proposed new car audio setup:

Factory head unit, speakers
Orion 2105 xp 400 watt amp bridged
Lighning Strike 1 Farad Capacitor
Factory sub enclosure (modified so its sealed)
Memphis MC104D sub

I already have the amp and capacitor, I can not afford to change those or the head unit. However if someone knows of a similiar sub in the memphis's price range ($100-$140) that would perform better for sound quality purposes please let me know. Thanks for your help.

edit: I got some model numbers mixed up... whoops