With that light controlled room with dark ceiling and walls there is no need for a gray screen. I have 110" Jamestown screen Cinewhite (1.2 gain I think) with my HD33. You will need the gain for 3D although it might be a bit bright for 2D. I have a ND2-400 filter for 2D although with about 2400 hrs on the lamp I don't need it that often. Unless you watch a lot with lights on a gray screen would hurt the whites.
"Smart enough to know better, to old to care" ------ Dedicated Home Theater, Mitsubishi HC7900DW Projector, 110" 16:9 Jamestown screen with variable power masking for CIW 2.50:1 to 16:9, Marantz 7009 with 7.1.4 Atmos with Ohm mains,3 DIY Subs (2 15" (1 ported, 1 sealed and a 12" 4th order bandpass), 1 DIY butt kicker, Custom Built HTPC, 10TB DroboFS NAS