If you can get your hands on a Revel B15 for say around $1200.00, it is a sub that is well worth the price. I picked up one about two months ago and truly could not be happier(unless I had two B15's) with it. It literally can blend seamlessly with your fronts and virtually disappear in your room. I never new a 15 inch sub could be so tight and fast like a quality 10 or 12 inch sub. Very musical and great for HT.
On another note, the Revel Sub15 is considered one of the better passive subs ever produced.
Bill