I'm using an LT-150 on a homemade screen (roughly 1.3 gain) that measures 50 x 90. Brightness is plenty fine.
IMO, if you have total light control, brightness isn't the issue. Other issues will prevail. What size of room are you building? How far back will you be sitting from the screen?
Since I started the quest for the perfect home theater, I discovered one thing: my idea of a proper screen size has been shrinking. When I saw my first FP, I was so blown away by the big screen that I had the notion that bigger was better. And I like sitting in the first 1/3 of a movie theater, so I like my images big.
So when I started, I was going to build a screen that was 100 inches wide. But I decided it was too big for the room I'm building, which is 12 feet wide and about 19 feet long. So I decided on 96 x 54. After doing more research, I reduced the size to 92 x 52.
I finally received my LT-150, and built my screen last week. I decided to make it even smaller, since a number of people recommended more like 84 x 48 or so. But I couldn't shake the notion of wanting a big screen, so I built it to be 90 x 50.
Now I'm wishing I had made it a bit smaller. From my desired seating position of about 10' back, I find the picture to be just a bit overwhelming, and any jerkiness from the PC DVD player bothers me. If I move 2' farther back, the picture becomes much more watchable. This has nothing to do with screen door, because on the LT-150 you really can't see the screen door from 6-7 feet back or so. It just too much picture. It's plenty bright, but fast action just becomes a bit too hard to follow.
I think the difference might be the quality of my output hardware. I don't have a progressive-scan DVD player, so I've tried both an HTPC with a Matrox G450 card and the Matrox DVD player, and a Sony DVD player using S-video. The S-video makes the picture look a little fuzzy when sitting close, and the PC DVD player makes motion look a little jerky. Perhaps with an excellent HTPC setup or a good progressive-scan DVD player I could move back to my 10-11 ft desired seating position, but until then I have to sit farther back.