This is an older thread, but I thought I'd share my experience witha new 159" High Power and HD3300. The center of the screen is about eye level when sitting maybe a little higher, and I mounted the HD3300 (DLP 3D projector) about 30" above my head, maybe a litter higher. The brightness for 2D was a little too much and I had to tweak it down (this in eco mode). For 3D, I also tweaked the brightness and contrast down to a better level for blacks than I had it previously for my 142" DIY 1.2 gain screen. The brightness for this huge screen is fine; and even with a high level of keystoning (+6), I see no distortion or annoying resolution issues. I watched Titanic 3D last night and wow, wow, wow is all I can say. I had a 2.8 high power a couple of years ago, but wasn't happy with it--too much yellow bias and sparkles. The new 2.4 high power is crystal clear, no sparkles or noticeable color shift, plus a wider gain angle--I absolutely love it. When I stand up putting my head near the lens level, I see a little brightness boost, but not enough to make a difference. I would say I'm getting about 1.8 to 2 gain at sitting level. I sit about 17 feet from the screen, and the projector is mounted about 18.5 feet from the screen.