need recommendations for sub for music


Hi Everyone,
I recently completed my HT set up with a Sunfire HRS. I love it for its power, tight and clean bass and compact size. But I thought I'd get another small used Sunfire (the Junior, for example) to complete my 2-channel mostly music set up in the family room. It has to be small and cannot be placed in a corner, unfortunately.
But I also wonder what other subs are out there to best complement my system. The family room connects to other rooms in a very open floor plan. I have the Denon AVR2808ci receiver and a pair of Paradigm Studio 60s. The set up is mostly for music.
I have a small budget, so I am looking for a used sub on this site.

Thanks for your suggestions
dogmatix
After B&W, HSU, Energy, Sunfire and Paradigm my current and still favorite is the Velodyne DD12.
Depends how much you wanna spend. The velodyne dd12 is a nice sub but kinda expensive. A velodyne hgs 12 is a liitle cheaper and is the same sub without the room correction I'm pretty sure. I think that either one of these subs will sound better than the sunfire. If you can afford a jlaudio sub get that. Best sub out there IMHO.
Thanks, folks. I will be able to seriously consider any brand (if second hand) including Velodyne, JL Audio REL or Revel.
I'd appreciate specific models you recommend that are truly musical. Most of my music is from the cable channels. I think I may need something larger than a 12" woofer, though. It is a large area I want to fill. From your responses, I realize I may also need a unit with room correction for sure, so that helps.