1. You can get a phenomenal projector for between $2K and $3K. The $10,000 projector you looked at, likely had the same DLP chip in it that you will find on the $3K Sharp Z2000 projector. So, the question really becomes "What are you actually getting for the extra $7,000?"
I did a side by side comparison (a-b test) between a $15,000 Runco and my personal $2,000 projector 3 years ago. Did the Runco look better? Yes! Did it look a LOT better? Not really. It looked marginally better, which is just ridiculous for a $13,000 price difference.
Anyway - the Panasonic AE900 and the Sanyo Z4 will be out in about a month and should be near the top of your list. They have highly adjustable mounting options. You can mount them completely at the rear of the room... or if you have behind the wall access, you could mount them behind the wall and project into the room. They both have full 1280x720 resolution, which means they carry the mark of being a true 'HD' projector.
2. Screen door effect exists on all fixed pixel display devices and is more accurately called inter-pixel gap. It is the very small space between two adjoining pixels where light is not able to shine through or be reflected. It exists on DLP, LCD, LCoS, SXRD, DILA, etc. projectors. Basically ALL projectors except CRT projectors have screen door. The question is, how close do you have to be to actually see the screen door effect (SDE). Well, with lower resolution projectors (853x480 like Optoma H31 or InFocus SP4805) or very poorly built projectors (business projectors) you may see the screen door effect anywhere closer than 2x screen width.
Well designed projectors like the Z4 and AE900 or the 1280x720 DLP home theater models will allow you to be as close, or closer than 1.5x screen width and not see the screen door effect. This is especially important as THX optimum viewing distance is 1.54x screen width for HD material.
In a nutshell? Get a decent 1280x720 projector and you won't be worrying about SDE.
3. Screens that roll up into the case develop waves in the fabric. All of them do. I have yet to see one, from any manufacturer, that does not develop waves. The only time they don't develop waves is if they are tab-tensioned (see photo below). This effectively keeps the screen flat and allows the screen to roll up into the case and out of the way. Perfect for the family room - worthless in the theater. Especially since a tab tensioned electric screen typically runs well over $2,000.00 while a fixed screen for under $1,000 can give superior results.
Superior?
Sure! You see, a permanently fixed screen of decent quality will come with a nice durable aluminum frame that easily bolts together. The screen material will bolt to the back of the frame and the frame itself will be covered in velvet which does a phenomenal job of absorbing any stray light that may hit it and properly frame the image which gives it more punch.
In a room like you are describing, going with a 100"+ wide screen and a couple of rows of seating seems possible and can turn out fantastic depending on the level of work you put into it. Whether it is contracted out to a pro, or a DIY job, having a large open room with no ambient light issues is key. From there, it is about getting the right stuff in there and getting it all set up for optimal quality.
Have fun! And, as said, spend a few hours/days/weeks reading through things over at
www.projectorcentral.com as they have some excellent reading for you on projectors specifically. Then come back here for all your additional questions.
