Subwoofer recommendation

Looking for a subwoofer to go with a pair of Coincident Triumph Signatures. Got the speakers when I had a pair of Rogue M-120's but had to sell because of a move and space. Now I pretty much use them for movies, but would like to up the bass with a sub. Looking for something in the $500 range.
Hsu Research.
Not enough info, how big is room? Also, where do you plan on putting the sub, or is this flexible?
in my opinion, the best subwoofer for the money is the Sunfire Subwoofer. it comes in several flavors and sizes for just about any applications. The best is the signature that is 13 x 13 inch cube. I install home theater systems for a living and I have not met a subwoofer for the price that will shake the room as well. 2 are better than one, but one will do the job nicely. Nuff said
I've been through a few subs; Paradigm, B&W, Defenative Tech, Infinty, etc. and never could find one I really liked for music and HT. That is until I took a chance and ordered a SVS 20-39PCi. All I can say is wow, what a great sub. My wife hates it because it looks like a big industrial tube with black carpeting on it. Not pretty, but hare to beat dollar for dollar IMO.
My Vote is a VMPS subwoofer. I have one and love it!!
Twice your budget- but the Axiom EP-500 might be a good choice.
The Outlaw LFM-1 is an amazing sub for the price.
I have a 15" sound Dynamics with a mosfet amp. The thing is loud and boomy.