I have a Velodyne DD15. Its a mother. The big advantage of the better Velodyne subs is that you can tailor the response to your room, so in my case its tucked down the side of a settee away fro the cats claws. You connect it up to your TV and adjust an on-screen display.
Jerry
Hifi: IPL transmission line floorstanding speakers, Squeezebox Touch, Denafrips Ares 11 DAC, DCB1 Pre-amplifier, Croft Series 7 power amp.
Custom Hifi cables HA10SE headphone amplifier and Hifiman HE-400 headphones.
AV system: LG 55B7, Denon AVR -x2300w receiver, Quad 12L (front) 11c Centre and 11L rear . Velodyne DD15 subwoofer.