I have owned Velodyne HGS as well as the DD series. I also currently own SVS (1x SB 2000 Pro - 1x SB4000 - 2x SB 16 Ultras).
I run a 2 channel system now. The Velodyne is a much better sub than the 2000 - no question. Is it ‘Better’ than the SB16 Ultras? Sort of, and sort of not. They are a bit different.
That said, if you are using the DSP on the Velo, you should stop. I could only get that sub to sound right the old fashioned manual way.
Most others are correct. The plate amps on every single Velo I have had fried. Cost me $208 back then to repair from Velodyne. No clue what they charge now.
BTW - SB16’s are a lot more spendy then amp fix. They are very close in terms of SQ. Output though, the SB16’s kill it. They go about their business very different.
SQ on the DD series is excellent and integrate very well with higher end speakers.
IMO the only thing new that compares to the Velodyne’s would be Rythmik. They are also Servo Subs and have to be set up manually without DSP. Although I did eventually go with the SB 16’s for ease of use and there was only about a 1-2% difference in SQ - to my ears.
I vote repair as the DD is still a very, very good sub. They are also making subs again. May want to give them a ring.