I'm thinking about buying a dalite model b screen but a lot of people say it's not good if you can't control abient light? I have a loft with 13 windows and have blinds but the room is still somewhat "light". What I want to know is how much light is to much light?
Give Jason at AVS a call, I bet he can beat these prices. Also consider www.cousinsvideo.com as free shipping in US and their prices are usually very competitive. If you have a lot of light and are using LP-425zb (900 lumens--artificially high, I bet it's more like 600 lumens), I would go with hi-power 2.5 gain screen if you can't get your room dark. Stay away from glass-bead as it's too grainy and can't be cleaned easily (glass beads may fall off when rubbed). Have you consider DIY screen using blackout material (gain of about 1.1) stretched on wooden frame? It'll cost you less than $50 for the size you're looking at--well may be a little smaller as 54" width is the limit of the blackout material but length is not limited. I have a 54"X96" which is 16:9 ratio DIY screen and it's comparable to 1.1 retail Bretford (another brand) manual pull-down screen. I actually like my DIY screen better as manual pull-down screens eventually gets wrinkles or waves due to rolling up and down. Most people leave their pull-down screen down permanently to avoid these problems. Some even tack it on the wall for perfect smoothness. I use bungie cords to keep the screen under tension to rid of wrinkles or waves.
With that projector output, you should probably consider something like the Da-Lite high power. You should contact a Da-Lite distributor and have them send you a sample pack of screen materials and check for yourself. As Huey mentioned, check with AVS and http://www.cousinsvideo.com.