Subs with focal katna 3s

@paliden done any RTA to know where specifically in the bass the deficiencies are? Room nodes and anti nodes are inherent. You can’t bypass physics.

Also outside of classical, most of the genes you’ve listed whilst have some deep bass passages, just need 50Hz at good SPL

 An RTA at your listening position will tell a lot and help remove the unneeded guesswork 

I'm running Sopra no2 with a pair of JL Fathom 112V2s.  Very happy with the sound in the room.  Maybe look somewhere in the JL subwoofer range?  

You didn't mention anything about your Preamp so it's hard to know what the best sub options will be. 

What’s your budget, do you require built-in software to help with setup, and are you looking for new or used?

System is upstairs is bryston preamp, dac, and roon/ quobuz streaming.  EAT flat turntable with ortofon black cartridge.  14b3 cubed amplifier.   I have an arc Mike and software I used with my downstairs anthem avm60 surround sound system but didn't know if it would mesh with the bryston two channel music set up.  I will take suggestions on a stand alone diagnostic device.  My cinema setup had goldenear Triton reference mains pushed by parasound a21s (2) with a carver sunfire cinema grand for goldenear aons as surrounds(4).   I know it's all ss with tubes, but that may be next experiment.   House built in 1923,wood floors, 10x18x36

System is upstairs is bryston preamp, dac, and roon/ quobuz streaming.  EAT flat turntable with ortofon black cartridge.  14b3 cubed amplifier.   I have an arc Mike and software I used with my downstairs anthem avm60 surround sound system but didn't know if it would mesh with the bryston two channel music set up.  I will take suggestions on a stand alone diagnostic device.  My cinema setup had goldenear Triton reference mains pushed by parasound a21s (2) with a carver sunfire cinema grand for goldenear aons as surrounds(4).   I know it's all ss with tubes, but that may be next experiment.   House built in 1923,wood floors, 10x18x36

You really want two sealed subs.  Arendal seems to offer high quality/$, and they include a setup app and a 60-day “risk-free” trial period (although I’m not sure of the details).  Worth looking into I’d think.  If you don’t require a setup app then Rhythmik offers a lot of performance/$ and a 45-day trial period although return shipping not included. Best of luck. 

@paliden 

We have REL S510s with our Kanta 3s in an open floor plan family room. They are definitely worth it. If your floor is a suspended wood floor you will need some isolation under all speakers. Good luck !