JL Gotham F212 v2 vs ?

For two channel, there is no substitute for REL subs. As others have pointed out, a pair of S/812 would be the way to go.  

@smodtactical --

This is a pricey but seems to be a high quality well made sub. This is for a future listening space that would be 20x30. For some real power but control is there any other subs to consider at that price point or lower?

For my money the Gotham’s are simply too expensive, period. I’m sure they’re excellent subs (and, seriously, you’d want at least two of them, so do the price-math on that), but it’s high-end audiophilia moved into the subs arena with all that entails in exotic finishing and an overabundance in areas that aren’t strictly serviceable for bass capacity and overall quality.

You can get a lot more a lot cheaper, and with bass quantity in abundance translates into headroom which in turn equals lower distortion (= better, cleaner and more effortless bass), and finally their number, potentially in quads (placed spread-out) will minimize room modes to where PEQ is hardly needed.

The PSA sub mentioned would be a good choice, it seems, and I’d consider the vented twin 21" IPAL option as well. Both options will provide in-room extension and SPL to die for, and their number in quads would cost you roughly the same as a single Gotham V2. Any which way you bend this the quad PSA options would obliterate a single Gotham in quality/quantity.

If you care to investigate a bit further, and keep an open mind, I’d look into horn sub options as well. Why? Because bass horns sound different compared to direct radiated bass, and by ’different’ in this case and to my ears, I mean better. Quality horn bass appears smoother, more present, effortless and enveloping compared to DR’s, and just flows into the music very organically and viscerally. An interesting option here would be the JTR Orbit Shifter LFU with an 18" unit per horn, which is a classic Front Loaded Horn (with the driver hidden inside). You may give up a bit in extension compared to the PSA’s, but still have usable output to a claimed <10Hz in-room - more than sufficient for most any situation. 4 of these in the future space allotted to you would be quite the experience, I’m sure. Oh, and they’re only $3,000 a piece..

https://data-bass.com/#/systems/5c1d5aff45bca300046104e0?_k=vg02vq

For the price of the Gotham F212 v2 you can get 8 HSU  ULS-15 MK2 Subwoofers and still have money leftover for top of the line cables.

No absolutes in audio, only preferences, but I do want to share my experience with subwoofers. I've owned the following subs: Martin Logan Depth I, HSU(can't recall the model), SVS SB15 & SB16 Ultra, Dual JL Audio F110 v2s with the JL CR-1, JL Audio F112 v2, and now dual REL Carbon limited subs. To my ears, in my system, the REL Carbon Limited subs are the only subs that have improved everything across the entire audio spectrum. The RELs totally disappear and have taken my 2-channel to the next level. 

So it sounds like Rel is the main competitor to seriously consider. I like the arguments you guys make about many more subs to smooth out modes.