Wherever you want to sit is best, and you can always do that at home. I like to sit close - 1 to 1.5 screen width away. On a 65" plasma I might sit 2 meters away.
As long as you can just see the side edges without turning your head and the image does not look grainy you are not too close.
You are probably not too far to loose any content detail if slightly less then 2 meters and at 2.8 meters the amount of detail lost would be small.