I was interested in Velodyne subwoofers when I was buying my AV kit, but my local Sevenoaks did not stock it. So no, I've never heard them.
I went for the Monitor Audio AW12 which is a brilliant subwoofer in every respect. Even B&W PV1 has received excellent reviews & it also sounds nice, but for me, I preferred the AW12 which sounded more authoritative and had that extra 'oomph'. I thought the PV1 was a little overpriced.
Other subwoofers which came highly recommended to me were
SVS &
BK. They're supposed to be very good and some audiophiles claim them to be the best available today for the price. The only problem was, I couldn't find any shop where I could audition them.