My room is 38x16. When I put in the theater room I wanted to go a minimum of 120". But was talked out of it. You can guess by who.
. Every time I went down there I was disappointed. So after 3 yrs of that I decided to do it my way. I now have the biggest screen I could go with and still have an awesome picture. What size you ask, 159 inches!
My projector is a Mitsubishi HC6800. I agree with the previous posters, I would go as big as I can and still have a great picture because in the long run you'll be disappointed if you don't.