JL Gotham F212 v2 vs ?

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. 

m-db,
Thanks for the kind words. I agree with the comments, "There's no right or wrong, "we may exercise more agency, assembling a system that presents the music just the way we like it, and in so doing, participate in the act of creation?" It's about personal preference. As a matter of fact I don't use the high-level connection with my REL subs. I purchased  upgraded speakon cables and compared the high-level connection to the low-level connection. The high-level was connected via SignalCables speakon cables and the low-level via Audioquest Husky RCA subwoofer cables. After a week of listening I preferred the low-level connection...more dynamic and tighter bass. The subwoofers still disappear more than any others subs I've owned. 

My friend has dual S/812 with Raidho C3.1 speakers and it sounds good. I've never heard the Gothams or No. 25; therefore I can't provide any advice. I have the choice between dual REL Carbon Limited subs and a single No. 25 and I chose dual Carbon Limited subs.