Viewing position is 5 feet off glass wall and 5 feet from wall behind, meaning distance to screen is 14 feet.
Agree with Kennyt. At a distance of 14ft bigger is definietly better. You should go as large as you can in your price range.
In your price range consider these plasma tv's at Amazon:
(Amazon has 30 day return -free shipping)
Panasonic VIERA TC-P60ST30 60-Inch
Samsung PN59D6500 59-Inch
Let us know what you get and how you like it.