My thoughts exactly seeing the first owner's room. Those speakers need room. They look about as big as the Arrakis which, having heard many times really breath well with 12' ceilings and in a ~650 sq ft room. The sound stage is reproduced from the floor to the ceiling depending on source material. I'm fairly certain the 12' ceiling partially enables this. Of course, I still wouldn't turn down a chance to hear the M9s in a vertically challenged room
Sure, if someone is building a room for large speakers then you build out 11' foot 12' ceilings. Alon has done this in Hayward, we are also doing this in Dallas.
BUT I am installing the M9s in my place, which only has 10' ceilings because there are a LOT of customers that only have 9' or 10' ceilings. I want to see how they work. I've also installed 10+ Goldmund systems that were 77" high. In one case the customer had an Ocean home and the listening room was in the basement with 84" inch high ceilings. He wanted to try it, so we did it.
He kept the speakers for 15 years and listened to them every day and loved them. All kinds of music. Would they sound better in a larger room, SURE. Did he have a larger room where he wanted to listen, no. Did he understand all of this prior to installation, yes. He had owned the large IRS in the past and understood large speaker installation.
I've installed hundreds of speakers in the last 50 years. I would say maybe 25% had ideal room dimensions. A LOT of customers that have the $$$ and want larger speakers only have X amount of room. They still want large speakers. They understand that they won't sound the same or as good as if they had a larger room, BUT they still can be made to sound REALLY GOOD and acceptable for them to enjoy listening to music.