Subwoofers for Martin Logan CLX's

A good friend has Martin Logan CLX’s He is looking for new Subwoofers currently runs top model REL’s but they are getting older (10 years+) now and he has the desire to upgrade. Current REL prices have gone up quite a bit for what he wants. I think he said they went from $9k to $14k each for the model they recommend for the speakers/room size. He needs two but is having issue buying due to the current pricing/tariff’s etc increases (about 35% here in Canada). He’s also considering the new, yet to be released, Logan Subs. But they have not given details on when they maybe available.

I told him I’d ask you fine folks what top model sub’s are now out there that would be a good match to the CLX’s. Noting he’s not interested in lower end models. His system is in the $300k range so matching gear is top quality.  He is not looking at the largest Rel’s I think he’s considering the ones just below for size reasons, he’s in a smaller room, 16’ x 18’ I believe but it’s a dedicated and treated room.

Any suggestions for subs, lets say in the $8k-$20k price range?