Brett, just am now ordering my second Stewart electric screen. Having has a electric 100" 4:3 Greyhawk, I can say that without a doubt it will help with the 13HD, not hurt. The build quality of don's screens is remarkable. Da-Lite and others make nice screens, and i'd own one if I had never seen a Stewart screen, but I have! Having said that they are simply the best! In your room I'd go Greyhawk as everything is well controlled. I will be getting a 106" 16:9 92" x 52" electric FIREHAWK with the 13HD only because of the ambient light into my family room.
Last thing, call Jason here at AVS for your screen. He and AVS are the best to deal with, great pricing and great customer service.