I guess when you say hi end sub do you mean hi end for 3-5k? Or less? Or more? :)
1k? = REL T1 It's increadible... you may not need to look futher? Slam reliablity, fun, easy to set up... and some how intergrates into any system? How? You say? Long answer but worth finding out.
3k ish = REL Brittania B1 (I'd get two of them... rel prefers 3 per room... they come set up for an amazing way to to divide all three)
4k = Thiel SS2 (Use two...) Well yes it's on the audiphile level of sub, but the fact that your loins will shake while ever so gently tickeling your ears like some one put a feather in it isn't so bad either.
I actually really enjoy the Theil SS3 Sub. Although it's no longer made it will almost pick up your house and walk away with it. But for a budget just get 2-3 rels (t series or Brittania Series) and you'll freak anyone who comes to your house and watches U571 (Depth charge scene) to running out of the room and crying like a baby in fear.
I just might do that right now... My neighbors dog keeps barking..