I can heartily recommend the SVS PB10. It might be low end for SVS, but it is one helluva sub for the money. Ken's first words upon walking in were "I can tell something substantial is here."
It's performance is really amazing, especially given the price. Strong to 20hz (to 18 in my room), authoritative and effortless deep bass in movies and fast, tight response to music.
Now I really want to hear a Hsu STF-2 to see how it compares - cause I can't imagine bass getting any better at this price point.