To the OP:
To find your answer go here:
http://www.projectorcentral.com/Sony...ulator-pro.htm
The projection calculator is interactive. You will have to input the throw distance, screen gain, aspect ratio, size of image that you want.
The calculator is based on obtaining a luminance of 18 foot-lambert on the projection screen. (The foot-lambert is used in the motion picture industry for measuring the luminance of images on a projection screen.)
PS. You can select the other projectors you are considering as well and see the results.