Back to my opinion without worrying about a price range (which someone is bound to ask) I think the new Digital Designs T1508 or T1510 subs can take a ton of power but really need ported boxes to reach their maximum potential. If you are talking sealed boxes, i would recommend the old school JL audio 10w6 or 8w6 both are regularly found in the classifieds and on
ebay. I am actually running four 10w6's sealed right now, and i have two others laying around if you are interested! But you cannot compare JL and DD, its just not fair to JL.