I hope this isn't a repost, but look at this.
http://forum.carstereos.org/showthread.php?p=603831#post603831
http://www.acoustic-visions.com/~acoustic/products/subwoofer_drivers/index.shtml
http://forum.carstereos.org/showthread.php?p=603831#post603831
http://www.acoustic-visions.com/~acoustic/products/subwoofer_drivers/index.shtml