@m-db - I’ve owned many Velodynes over the past 20 years, in both home theater and 2 channel configurations. My first was an HGS 10 back in the late 90s and most recent were DD18s.
They all sounded great at the time - those are fast, punchy subs. But I’ve also had power supply and/or circuit board issues over time. Maybe I had bad luck, but Velodynes have not aged well for me. They seem to have a 7 year or less useful life before needing major repairs.
Back on topic, I use old-fashioned trial and error to optimize speaker placement in each room. I hear more detail and ambience (especially in percussion) from the RELs than any other sub I’ve trialed or owned. The best way I can describe it is that the RELs, when properly configured, dramatically widen my sound stage and open up recordings in a way that I really enjoy.
It isn’t about bass - virtually any sub will give low bass.