You really are going with a 4:3 screen.?
Why not CIH 2.35 or 16:9? 4:3 is only recommended if you watch a lot of SD television IMHO. If this is for movies, video games, HD TV, Widescreen SD Movies, HD DVD, etc, go with 16:9 at a minimum. This will bring the bottom of the screen up.
You will want to check with the riser height calculator sticky that you will good to go from the back row and that you have room for your center channel speaker (preferably above the screen).