i'm thinking of getting a widescreen RPTV soon. i've got a viewing distance of 8-9 feet from optimal viewing position...what's the best size TV for this? i know there's a formula, but i can't remember it. i was thinking in terms of maybe a 51" screen, but i'm afraid this would be too big. also, i may be moving in the next 6 months so my viewing distance could potentially increase. what would be the best thing to do?