I just saw your Virtual System, those are awesome looking speakers in a beautiful space. I can imagine their sound, and suspect you are chasing something you don’t really need as audiophile1 implied, or said, not needed for him.
I mentioned my friend. He listens here, thinks he might need a sub. I agree he needed a sub in his prior space, however, we listen in his new smaller dedicated listening space, and I love his system, and always advise that he has enough bass, he could lose what is wonderful now.
His current space, I would first try a pair of reasonably sized stereo subs, pair of 8’s, 10’s? he is still thinking single monster driver. Years ago he built a table/sub with 18" woofer for the larger room, blew some amps, never got something he loved.
Send photo of your space to Martin Logan and KEF, that will help them help you.