As long as you have daylight, the image will be washed out. Projectors cannot create black. Look at the screen area under the conditions you plan to view in. That is as dark as your image will get. It doesn't matter how many lumens you throw at it, all you will have is brighter highlights, but there will NO dark scenes and very little, if any, contrast.
Your best bet if you want a GOOD, viewable image, is to use a flat screen. And the added benefit is that you will never have to worry about lamp replacements.
That's my 2 cents on the matter, other people may have other opinions.