I need a subwoofer/sub-bass opinion from you


Hello All--

I have a large room (well large to me).  It's 20' long, 15 wide, and 10' tall.  I run either Klipsch Forte IIIs or PSB Imagine T2s through a tube amp.  I have plenty of volume with either loudspeaker.  

What I want to accomplish is to add sub bass.  I did this previously in a smaller room with a Sumiko S5 (I believe it's the same or similar to the REL T5).    When I had the Sumiko dialed in, the system congealed into a wonderful sound.  There was no noticeably appreciable sound coming from the sub.  Instead, it merely filled out the lowest octave and added space, dynamics, and really made the highs seem less harsh.  

The Sumiko S5 does help in this setup but it's just not enough to charge the room or at least add enough.  

I'm thinking REL.  Thoughts? 

PS  When I ran the Sumiko, it sounded clearly better when I ran it off the amp speaker outs than off my Primaluna's dedicated subwoofer out. 
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One of the things that attracted me to my RELs other than the deal I got buying them, is the "high level" input system from the amp, which allows a reproduction of the amp's tone and doesn't require long runs of single ended cable...simple speaker wire does the job. This series of RELs also has adjustability to fine tune the phase, crossover points and level that newer versions may not have in as much detail. Also, although I haven't tried newer versions of RELs, I can say the "Q" series I own sound spectacular within their limits...and those limits (low frequency range and level) are well within what's needed to charge the room with controllable bass for music...I have swapped in my 92 lb studio sub that's flat to 19hz, and found that extra low range didn't improve anything relative to what the RELs are doing with the music I like...plenty of drive and heft with the RELs.
I've done a lot of research on subs.  Hsu Research makes a fantastic product.  Recently, I e-mailed Hsu regarding several technical questions and I received a very thorough and very professional response, as well as a recommendation that I add a high pass filter.  
I highly recommend purchasing Hsu products.  
"I highly recommend purchasing Hsu products"
Have you listened to Hsu products? I haven’t - only my existing single REL R-328, which sounds great for me.

But I’m upgrading - below are the candidates. Pricing is per sub if purchasing dual (SVS will -$100 from the 2x total). REL is not on the list: they’re over-priced compared to these competitors, of which the PSA’s are the priciest.

The HSU and PSA models use paper drivers, not aluminum. Does it matter, objectively? I don’t know.

The Rythmik and HSU models appear to support speaker-level line in. Comparable to REL’s fancy-pants Neutrik connection? Maybe.

sub | $$$ | driver | amp | freq. | size | spkr-level input?
Rythmix F12 | $893 free ship | 12" aluminum | 370w rms class A/B servo | 14-100Hz ±2dB | 15.75x15.75x17, 62lbs | yes
Rythmix F12-300 | $700 free ship | 12" aluminum | 300w rms Hypex servo amp | 14-100Hz ±3dB | 15.75x15.75x17, 57lbs | yes
SVS SB-3000 | $999 free ship | 13" aluminum | 800w rms class D | 18-270Hz ±3dB | 15.6x15.2x17.8 | 54.5lbs | no
HSU ULS-15 MKII | $779 + shipping | 15" paper | 600w rms class D | 20-200Hz, ±1dB | 18x18x18, 65lbs | yes
PSA S1510 | $1,300 | 15" paper | 960w rms class D | 19-200Hz
±3 dB | 17x17.25x18, 63lbs | ???