A lot of the thread traffic in the last couple of days centered on things like :
- is my 8 foot wide screen too big for 12 foot seating distance ?
- is Randy's 10 foot wide screen too big for 14 foot seating distance ?
I think your 50" will be fine
Seriously, the rule of thumb for seating distance changes depending on the resolution of the TV and the image you are watching. If you are watching a lot of standard definition TV then you might still want a viewing distance something like 3x screen width, which would imply maybe 47" diagonal, but for DVD and HDTV you can sit closer or have a larger screen.
Honestly, I think the 50" would be fine even for watching mostly standard definition (SD) TV. For DVD and HD it's a no brainer, go with the 50.