Finally bought my subwoofers...Sumiko S-10

I have looked at all the major players. SVS, Hsu, PSA, Rel, Rythmik, etc. I had a Rel Storm which I always liked the way it integrated. Therefore, I chose the Sumiko, which IMO is a clone of the S-5 Rel. The difference is the speaker material, one alum (rel) the other fiberglass(Sumiko). Both have 500/550 watts class D amp and 12" drivers and Passive Radiator. I ended up getting 2 of them, though that was not my initial plan. One may have been enough, even though my room is 5K cu ft+.
These subs go deep. They are rated at 22hz but I have played St Saens 3rd organ sym with no trouble. That supposedly goes down to 16hz.The S-10's handled it very well.

I considered the ULS 15 from Hsu. But my experience with Rel and its magical interface with the main speakers lead me to the S-10. Plainly put, I like the way my main speakers sound with the S-10's. They sound much larger that they are. There are details I’m not sure I’ve heard before. The S-10's do everything I wish including plumbing the depths of the bass. There may be other subs which do as well. Some say others do better. But most of the reviews are from HT users. My system is a 2 channel stereo and even IF the S-10's don’t go as deep (I doubt it) they do everything right for 2 channel music. Would I buy them again? You betcha!
I use 2 older RELS (Q150e and a Q108II) and can't imagine not having these things. I also have a (no longer made) 92lb Mackie HR120 studio sub (has a down firing EAW 12" and a 12" passive radiator on the front) that claims to be flat to 19hz, and it is. I use that one in a music studio and it does get abused from time to time, but for hifi the RELs impart a magic that works amazingly well, and the "high level" input is cool…although that required some adjustment when I switched to 99db efficiency main speakers, but no biggie.
Wolf. The speakon cable is a different animal for sure. I had trouble with a hum at first. But it didn’t sound like a ground loop because it increase in volume with a volume increase of the sub. I finally found the fix on the Rel site. They suggested tying off the black (ground) cable and using an RCA cable plugged into an unused jack on the back of my preamp which grounds the sub. it worked like a charm. The only complaint I have is that the volume & crossover dial has no detents which would help in setting volume/crossover with more precision. This is a minor complaint though and should not stop anyone from buying/owning one of these
BTW, these subs are discontinued due to the fact that Sonus Faber will be making these from now on
My Q150e has a ground lift that made the thing completely humless, and the 108II never hummed perhaps due to an anti-hum thing on its cable. I wire both with Canare cable and the three wire (2 positive, 1 negative) scheme to the Speakon plugs. I actually like the volume and crossover pots and use "chicken head" knobs on the volume pots as they show you where they are without having to pull out a sub. I use the subs in mono mode as they're different models and one gets put in a window for deck listening sometimes. Are you saying that Sonus Faber will be making REL subs? Interesting, but I've had such luck buying used RELs I can't imagine buying a new one. 
Thanks for the chicken head knob idea. My Rel Storm had course & fine adjustments on the crossover points. You could get the exact same point using that system. the round knobs make it more difficult. I suspect they are put on with a set screw. So, chicken heads, here I come.
Concerning Sonus Faber, my point is that the Sumiko subs are being discontinued. Thus I got a good price. However rather than being stamped with the sumiko name, they will be stamped with Sonus Faber hereafter. The Sumiko which I have have the hi level speakon connection and run at over 100kohm. The box is also the same size So, in essence, they are a Rel  S-5 clone. The cone material is different. But that is all that I can see that is different. 
Sumiko was the Rel distributor for many years. So I suppose they had the specs etc to build the Rel by a different name. Their literature says they were designed by Sonus Faber for Sumiko...all in the same family.
Recently picked up a Sumiko S.9 on clearance since they are being discontinued and wanted to add my experience.

The S.9 replaced a Rel T7 in my main system. It is slightly larger and more powerful (10" driver vs 8" driver) but it blends more seamlessly with my system. The reason being is the Rel T series have notched volume and crossover controls. My current amp (Nuforce STA200) is high gain (34.5db) and I was never able to get the perfect volume match with the Rel. Considering the difference in cost versus the T9i the S.9 wins out from a value perspective, plus it has slightly better low frequency extension according to published specs (25Hz @ -3db for S.9 vs 28Hz @ -6db for T9i) . Same principles for setting up Rel subs apply to the current Sumiko line. Mine is hooked up via the high level neutrik connection.

Nuforce STA200
Alta Rhea
Bluesound Node2
Sumiko S.9