There are two subs that I've auditioned that I can recommend.
1) Revel B15 sub
2) JL Fathom
They are both spectacular but big and what is fantastic about them is that they are magnificent for both music and movies. I own the B15.
You may also want to consider REL subs. Everyone that I know and respect speaks with the utmost praise about REL subs--especially for music.
I haven't auditioned Velodyne or PSB so I can't comment on those recommendations.