I was also lucky enough to hear the Wilson/MSB demo at Fidelis AV.I would love to demo Alexx with Momentum. I find Sabrina with Momentum / VAC SigMKIIa SE was more resolving and preferable but doesn't have the scale, slam ... size matters. The MSB mono is class A and warm side of neutral.
From a visual stand point the Alexx are definitely an acquired taste, but the sound was truly amazing. The soundstage encompassed the entire room and the sense of scale was really impressive.
Sabrina will be on my short list if shopping for speakers in a small room.