10" subwoofer around $500, used or new?

" Since you say it's primarily for music, I suggest you consider sealed subs. It would also help a great deal if you stated what speakers and electronics the sub will be used with "

Currently using JBL L5s and Cary Audio SLI-80. I may not stay with this setup though, so a sub that is not to picky (is that a thing?) would be a better choice.

Go REL or Sunfire.

Thanks Bob, the level should be variable (I assume you mean volume will impact the sub volume). And yeah no crossover in the SLI80, so the L5 will be full range. 

BTW are you affiliated with SVS?

Oh also, I may end up placing it on another system: Neat Iota & Bel Canto DAC 1.7 & REF S150. Iota high base is really weak, low base does not exist. Currently using a Velodyne DPS 12. Would the SVS offer a noticeable improvement?

Why settle for a 10" when for $539 shipped you can get a Rythmik L12, with not only a 12" woofer, but a servo-feedback controlled one?!