Thats a pretty decent size room. Personally I would go for the M60's in this scenario. JohnK has been enjoying his M22's for several years without the need to upgrade. But I don't think you'll get as good midrange as you will with the bigger, floor standing models.
I can't comment intelligently on the screen issues having no experience with any of that at all. I'll just say that if it were me contemplating this project, I would probably consider the fact that those specialty screens are specifically made for exactly what you're wanting to do, so they can't sound too awful bad. I wonder if you went down to a store that sells them if they would know of anyone who has one that you could demo? Seeing is believing.
