Thanks for the input everyone. Maybe my issue with the VP150 is just me. It's just that the M80's sound so good sometimes I feel like the center channel is lacking, especially since it plays such an important role.
As far as distance from the front wall behind the screen, I could probably move the screen out about 30" from the wall which wouldn't give me a full foot between the wall and speakers, but would be close. The screen is going into a little cove in the front of the room so it will be shadowboxed. If I move it out a bit the shadowbox would be less deep but it would give me the room. It might move the screen too close to my front row seating however. I'm still not sold on the acoustically transparent screen idea anyway because no screen is truly acoustically transparent, and I don't want it "coloring" the sound of my M80's. I've really got to give this idea some more thought. I've changed my mind so many times with the design of this room that it may never get started :-). At least I didn't take my current theater apart yet so I am not without my Axioms.
