velodyne dd plus? still considered best of the best?

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.

+1 on paradigm defiance.  Absolutely tremendous subs for music and movies.  I sold my E112 stacked pair (poor mans / smart mans F212 pair) and I am running just a pair of X12 Defiance subs and they are unreal.  Just as tight as the JL, around the same output, yet they’re made in Canada and have the best room correction around (way better than the F113 v2 I had).  
The only caveat is that they are boring square boxes.  Although the woofer does look very cool.

See if you can find a local dealer that will let you take them home.  They will shock you.