What Sub to go with Axiom M3ti speakers

I just got Axiom M3ti bookshelf speakers and really like them but I think they need some help with a subwoofer to compliment them. Can anyone suggest a sub that would go good with the Axiom's in the $400 to $500 range. This would be for a 2-channel stereo for listening to music (vocals, jazz). I have a Harmon Kardon HK3480 stero with a subwoofer out. I have a NAD C542 CD Player. My room has wood floors and is about 18' x 20' with very little furniture. I looking for accurate sound not booming bass. Thanks!!!

Just about any sub will work. But as always go with what your ear likes.

Velodyne
Hsu Research
Axiom
SVS - Great but it's a little HT oriented in this price bracket.
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