velodyne dd plus? still considered best of the best?

Hardly relevant anymore...David Hall, incredibly smart guy, invented LIDAR and sold it to the US Military.  Velodyne is a shell of what it once was and is barely in business.  Because of LIDAR, David certainly doesn't need to live on subs anymore.

Please take a look at the Paradigm Defiance Series Subs.  Start at $400 and go to $1499. Starting at $549 they have Anthem Room Correction which can be run on an Apple or Windows PC or a Mobile Device,  Full App Control of the sub from a mobile device; which allows you to find all the rattles in your room at specific frequencies by doing a "Sweep" (from 20Hz - 120Hz that you can lock and adjust in 1Hz increments) so you can isolate those things rattling at every frequency and know what frequency it is.  It also allows you to hear where the dips are in the room at those frequencies.  And finally, all those have wireless capability as well if you can't get a physical wire run where you need the sub to be. 

X-Series made in Canada from $999 - $1499 and V-Series made in China from $399-$649.  X-Series woofers have two US Patents = 1) Increases output by +3dB, so double the output, and 2) Reduces the distortion by 50%, so cuts that in half...Musical and Dynamic for movies!

 https://www.paradigm.com/en/overview/series/defiance-series   

Velodyne has not made a sub in a long time. they where good in their time, best in home theater. Good customer support, but not sure if they repair them any more. They have moved on from the sub business. I was at their factory 5-7  years ago and the sub was just a very small area of the plant and becoming smaller.  I had several of their subs with my last being HGS 18 for my home theater. Great sub. but i sold it a few years ago and have moved on to 2 channel only system. You should check if they are still servicing the subs before buying one.

How about this:  https://destinationhifi.com/products/legacy-goliath-xd-subwoofer?variant=336275489

Of course not

I wouldn't buy a powered loudspeaker from a company that no longer services them or provides warranty service....stick to something with good warranty, and run some good room correction software and it will sound as good if not better than some old Velos.