Which Subwoofer

I am a multi sub/swarm acolyte.  Upgrading my current dedicated media room, but will move one day and build from the ground up a room 2-3x the current size.  Anything I do will be moved to the new room.  The current room is 2200 cubic feet of space.  I have put together a 7.4.4 Dolby Atmos room.  Now that I have put accoustic treatments in the room the highs and mids are great, but my 2 B&W ASW610 just don't have the oomph of low end.  Yes, I installed several diaphragmatic absorbers (Acoustic Fields) to keep the room boom down.  I have started to add amps to use in the new room.  Current equipment

Denon AVR-X6700h
Anthem MCA 225
B&W in walls and in ceiling.
Will put the 10 inch subs in the rear corners

Possible upgrades for the new room 9.5.6, Legacy Audio Aries, Marquis XD Center, Silhouette sides x4 and Rear wall, Stratos 8 ceiling x6.  Will add an 18 inch sub in middle rear of the brands below and add another 2 of the subs below to the side rear.  Anthem MCA 525, and another 2x Starke AD4.320 amps.  Will replace Denon with Trinnov, Storm Audio, Acurus Processors.

Which of these two subs would you recommend?  I want something between SQ and SPL because I listen 2 channel, but not critically.  I just enjoy good music of all genres.  

Salk Rythmik G25 x2
Seaton Sound HP+ and HP-

Size matters so nothing bigger than 20" wide.  Height and depth not so much, but the two above meet all of my requirements.  I want something the digs deep.  I also want something that brings value.

Most of the deep extension and sound quality comes more from the number of subs than what kind or even how powerful they are. When going to a bigger room of course it will help to have both more and bigger. The size room you are talking something like Tekton 2-10 subs would be awesome. But they are too big for now.  

One thing you might consider then is to get everything on Pods and Podiums. You will be surprised how much room resonance (boom) is energy from the speakers direct into the floor and walls. Huge improvement. You will want this in the new room anyway. Just an alternative since it seems like you may wind up with some kind of compromise either way, this way it won't be with buying smaller subs you might just wind up selling later. 
Millercarbon, I already have my subs on isoacoustic platforms.  The new subs will sit on some diaphragmatic absorbers.  The tekton 4-10 and 2-10 were on the list.  They just don't have any frequency response curves.  I understand fr don't make or break a speaker, but would like to know that the go below 20hz.
Millercarbon Tekton says they are 20hz-120.  I want to see how they measure both anechoic vs in room.

Anyway Jim Salk recommends a 15 over 2 x12 or 4x10 inch woofers for digging deep.  He says you get a lot more low frequency.  I love your system and respect you knowledge.  I believe the 2-10 and 4-10 is better for music, but theater it is about size vs surface area.  I am about to buy 4-15, based on my 2 options.  Once I reach my next room I will have 8-15s and one 18.  Verses 16-10s. The Legacy Audio Aeries have 4-12s with 2 speakers.
We are also talking about
Seaton Sound - 4000 watts RMS
Tekton- 600 watts RMS
Salk / Rythmik out of the two you mentioned. You should also check out Power Sound Audio. Maybe a little more bang for the buck.
@big_greg from mybresearch Power Sound Audio is like SVS toward SPL vs SQ.  The S3012 does look very nice.  We are talking about almost $550 savings per subwoofer.  I would put the Power Sound Audio in the same category as Seaton Sound.  The finishes on Seaton just look better than the Power Sound Audio.
FYI Salk doesn't actually make the subwoofers.  They just take the order and forward it on to Rythmik company.

That being said, I would vote for Rythmik for sound quality when compared to SVS.  I don't know about sound quality on the Submersive.  However, it doesn't seem like it has a normal IEC power input so an upgraded power cord may not be doable.  Also, I would probably rather have an separate amp for each sub rather than a single amp for both master/slave.
Auxinput Salk makes the custom cabinets, but does use the woofer and amp from Rythmik.
Ah, I stand corrected.  I know there is one company that does exactly as I stated with Rythmik.  I assumed it was Salk, but I remembered wrong I guess.
Auxinput, no worries my friend.  I agree with you on the Seaton Sou d having one amp.  Many people speak highly of Seaton Sound, but Rythmik just seems to be the best of both worlds.
Jim Salk offers Rythmik Subs both incorporated into some of his loudspeakers and as stand-alone subs. He takes the F15HP DIY kit (as well as the F12) and installs it in an enclosure of his own design and build, and it is incredible! It is an extremely well-braced enclosure (it is pictured on the Salk website), 4cu.ft. internal volume to the Rythmik's F15HP's 3 cu.ft. Plus Jim offers really nice real wood veneer finishes, which Rythmik does not.
I decided to go with the PSA S2410 subwoofers for the rear of my room.  I ordered them 2 weeks ago.  Hopefully will be here in a week or 2.