I have no experience with the 20's or the 3.7, but I have found that the 3.6 and previous models needed to be played at reasonably loud levels in order to create an enveloping stage and create a dynamic sound. Are the more recent models less critical in this aspect?
IMHO, although not long ago the SoundLab A1 could be candidates for great sounding speakers in the $10k-20K, after the recent increase in price of PX models they are out of this race.
MY listening room is slightly bigger and accepts the Merlin VSM and even currently the smaller MASTER TSM very well. I can recommend them either with my Bernings or even more amazing with my Audio Consulting MIPA (mains independent power amp), although that is an admittedly expensive solution.
These speakers are really good, simple and satisfying.
Otherwise I would recommend Manger speakers as well, if you like the Manger units, that is ;-)
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Unhappily they are not manufactured any more, but every time I listen to the old B&W Silver Signature SS25 I find it a fantastic speaker, either in classic or rock. In a small/medium sized room they can play really loud if needed. Add a JL Audio F110 or similar and you are in Wilson/Revel territory.
FIY , I helped a friend buying an used pair recently - he paid around usd 3500 with the slate original stands.
I just upgraded/ordered to Zu Definition 4s---which retail for 12.5k now. They are now a true 101db at 8ohms. Very excited! Nano full range drivers ala Magico, a new supertweeter, and a downfiring 12" sub so the cabinet will be much stiffer.
I had considered selling my legs for science to obtain used Magico M5s for 35k---but I just don't like the fact that I can't use a 100 watt tube amp on them and I have no desire to implement huge ARC space heaters or the like in my room.
I also thought about Wilsons, but Maxx3s would really dominate my condo and could scare some folks.