User feedback on subs

While it’s not a path I want to go down, it turns out I need some subs for my cabin system. After trying lots of positions with little success, and after having discussions with people who’s experience and knowledge I respect, I’ve concluded it’s the only way for me to deal with some serious modes in an odd shaped room and to produce adequate bass in the large volume. Sigh.

Subs are relatively unfamiliar territory for me. Based on the conversations noted, I am leaning toward sealed subs - no ports/passive radiators -  to better blend with my main speakers. 

While I’m leaning toward REL #31s, also under consideration are Sonus Faber Gravis VI, Perlisten D series, and Martin Logan Balanced Force (now Depth?). All are subs I can get from dealers in my home state. The SF dealer also carries Paradigm but he hasn’t suggested any of those models - even their reference ones. While available at the same dealer who can provide Perlisten, I’ve ruled out JL Audio for reasons I’d rather not discuss here.

The SF have a high level connection very similar to REL - intuitively my preferred connection. SF and Perlisten (I’m unsure about ML) have an app which assists in setup though I’ve been reviewing enough setup routines that I “think” I’ll get better results with a manual process. 

The Perlistens are completely unfamiliar though appear well designed and solidly built. However, they do not have a high level connection which means I’d have to send my preamp feed to them and output from there to the amps. I have what I think is a very nice sounding preamp and I do not want to harm that purity. Perhaps my worry is misplaced. I have the same concern with the ML. 

All the subs under consideration can do what I need. But they are obviously not all equal. The REL is the easy (safe?) choice, though significantly more expensive than the others. The Gravis can be ordered to match the finish on my main speakers - not important, but nice to have. 

So - given the above, any user feedback on the subs I’m considering?  I welcome pros and cons.

Importantly, auditioning them in system is not possible as that location is a 4 hour drive each way from any of the dealers. So, I want to get it right. 

TIA