Hi JST,
Some excellent advice from others in this thread. Certainly, your large area and listening distance will demand higher output and three VP150s could provide that.
I'll describe my early experiments with the VP150: It was shortly after I joined Axiom and I was listening to most of the Axiom models in my home with an A/B instantaneous switching arrangement. (I'd point out that these comparisons were not blind as they are in the Axiom listening room.)
I was trying various combinations of Axiom's compact models (M2i, M22i) as centers and comparing them to the dedicated Axiom centers--the VP100 and VP150. One of my Axiom colleagues at the time, Joe Vassallo (after whom our Vassallo series of real-wood speakers is named) told me that he was using three VP150s as the fronts in his basement home theater, so just for fun, I flipped the two VP150s I had on hand and put them on stands, listening to them in stereo and in a home theater mode using a VP100 as the center.
I was surprised how good the dual VP150s sounded in the vertical orientation in stereo and remarked at the time to Ian Colquhoun that we should consider perhaps selling them to be used for special installations in a vertical orientation.
I did not do double-blind tests vs. other Axiom compact or floorstanding speakers of the VP150's used vertically. I don't know how they would have ranked in such a comparison, however I'd been doing a series of comparisons of the different models using both music and movie playback and I was simply surprised at how good the VP150s sounded. Joe Vassallo always claimed that his installation sounded great (I never heard it.)
That said, the in-cabinet M60s or M80s would give you all the output you'd need, and that's what I'd recommend. However, in terms of overall clean output at loud playback levels, using three of the in-cabinet or on/in-wall VP150s would give you the multiple drivers necessary to handle high SPLs and good sound quality (not as excellent as the in-cabinet M60s or M80s, I suspect) but pretty good.
Regards,
Alan
