you could get a used Paradigm servo-15 which would be the best for music because it's servo controlled. This also makes is the quickest sub, and on top of all of that it gets down to around 14 hz as it's F3 and that's in a sealed box. You could also look at SVSubwoofers and the HSU VTF-3. Also if you want it to go little bit louder but not quite as low, I would look at the Dayton 15" titanic from partexpress.com. You could buy it in kit form for under $700 I believe, or you could buy assembled for over $800. You wouldn't have to buy a parametric equalizer with this sub because it already has one in it's 1000 watt amplifier.

-Joey