Doing a little math per mdrew's information would yeild a max screen width of 101.382" or about 8'5". That means a ballpark of a 126" diagonal 1.78:1 (16:9 HDTV format) screen or 120" diagonal 2.35:1 (nice and wide) screen. Both have advantages and drawbacks. I have a 16:9, and end up with black bards at the top and bottom of my screen since most of the movies I watch are in a wider format that 16:9. So I need to "mask" off those bars to make them seem to disapear. Sirquack uses a 2.35:1 screen and some other cool technology that I am sure he can chime in on. When (if) he has to mask anything, it is the sides of the screen to make it not as wide, so to speak. Masking systems for me are a little more difficult to construct (thus I haven't done it yet), but for Sirquack, even some sort of side curtains would easily work.
Ok. With that said, those screen sizes are quite large. I am sitting about 14' from my screen (screen to my eyes, not to the back of the room), and 104" is pretty big.
You would also need a projector that can fire a good image that large with enough contrast and brightness. Check out
ProjectorCentral and play around with the projector calculators that show max screen sizes, brightness, etc.
You will also need to look at screen material and various gain numbers that will be impacted by room environmentals (ambiant light, etc).
Now for the TV vs. front projector. I used to have a large TV in my first home theater. For V2.0, I went with the front projector that I have now, and I will NEVER go back to a TV. There is NOTHING like the the really large display of a front projection system to really feel like you are in a theater.
As for 2 rows, you would be pushing it, but it isn't impossible.
My first home theater had 3 rows of seats in a 11 x 20 room. Now, the first row was pretty close to the front of the room, but again, it was a 46" TV and not 104". If you go with a little smaller screen, you can move the first row a little closer, and sneak a 2nd row in possibly.
For V3.0 of my theater, I said "screw the seating." 99% of the time, it is just my family of four, so it was really silly when I had 3 rows when 2 of them rarely got used. So now in V3.0, I am going to end up with seating for about 7 adults and no more. That accounts for the few times that the kids have friends over. Plus I am thinking about picking up some "Love Sacks" which are basically upgraded "bean bags" that can sit off to the side and be pulled out if needed.
Hope that this helps get you started.
