x1,000,000 on buy the sub alone and build your own enclosure.
I bought the Kicker CVR 12" with the prefab 1 cube sealed box. Granted, i thought it sounded alright. But, then i built a 2 cube ported enclosure tuned to 36, and wow! Huge difference. The only thing i would do differently would be to tune a bit lower, like 32 or so. But, all in all, i am happy as hell with the improvement. Prefab FTL.
If you want to see what that enclosure looks like, check my sig. Theres a link to some pics and vids! Good luck!