After trying or at the least seriously listening to them at shows "Either by early or late sessions to avoid possible crowding".
I auditioned them all.
And I do mean "All" of the offerings available on the higher end of the spectrum.
With the exception of that one "Krell" column. But knew I wasn't dropping ($50,000+) for a subwoofer anyway.
I decided on purchasing two for a stereo configuration from "Rythmik".
Each being servo-controlled and boasting (2 x 15") transducers. Which I then ordered and also paid for in full at that time.
And a month later I was forced to alter my plans, as rythmik finally told me that there was no way they could provide any of the products which I had ordered!
"I'll just sum up the experience as apparently there were; (Insurmountable problems with shipping and also inventory control issues of biblical proportion)".
"Yes", that really happened! But I believe now that it was all for the best, as things turned out!
I ended up going with the only subwoofer that had actually, "Wowed" me during my auditions. But a subwoofer which had at the time, just been taken out of production.
The "Martin Logan", "Descent".
With the three aluminum, (10") transducers in a triangular, vibration canceling cabinet. But of course, the model with the "Cherry" wood top option that I had chosen? It kept itself elusive and always, just out of my grasp.
Frustrated, and also because I had just so wanted "New".
I had then attempted to purchase the Rythmik offerings.
So finally I just found two "Descent's" all in black, which were used but with low miles. Both from the same fellow who happened to live near me for $1500 each.
Now I own (Seven) of them. All of them purchased as "used". And I could not be happier.
And I still audition subwoofers as I can. Just not at my home, most of the new offerings as they come out.
So you may wish to audition a used one of this type. And possibly save a few dollars in the process.
One last point. And regardless of what the sales team will tell you...this is true.
There are two, quite distinctly different, servo-control systems used in subwoofers.
And either is "Far Superior" in accuracy and "IMHO", also listening pleasure. Than any sub with "No", "Servo-control" at all!
But I still feel this is a huge difference! One system which uses a "feedback loop" and an "averaging algorithm" to, "approximate" through averaging - how it controls the subwoofer/s. "Like the one utilized in the Rythmik, GR research". And most "If not all" other current subwoofers".
And then there is the "original" servo-control system. Which is much more difficult and also very expensive to manufacture by comparison. But this system stands head and shoulders above the other in both speed and quality of the results gained. This system is "Like the one in this Martin Logan model", the "Descent"
Also, the "Martin Logan", "Descent" works quite well as a side or end-tables too!
Good Luck!