I have a long, skinny room with the screen at the end. Biggest I could do and still have speakers up there was 92" and I am very happy with it. I sit about 8 to 9 feet from the screen.
Of course, only one projector could make that small a screen at a 19' throw, and that was the Sanyo Z4, which I am also happy with.
I have a friend here who did a 100" that took up the entire wall and he's happy with that (about 9' seating distance).
Since it is a dual use room, I would recommend going with the better furniture layout. I think you will be happy with the 92" screen, even if you don't think so just yet
