@fire_water - I understand your frustration of not being able to audition the speakers extensively, I also had to buy without being able to listen to them as much as I would have liked to.
My living room is ~ 20' * 18' and is an open layout with an equal sized dining room behind and a longish corridor on one side. I haven't done any room treatments specifically and am sure much better sound would be possible from the Grimm MU2+ATC actives combination once I get the opportunity to do that. But they still do sound absolutely wonderful (and significantly better than my previous Naim and Audio Physic speakers combination).

