At 50 ft you're playing with fire, especially with 1080p. I see now you can buy (RAM has them) amplified HDMI cables. There's a 20m amplified cable, guaranteed for 1080p, for $265. I'd do something like that or fiber, or cat5, and never worry about length vs resolution vs various differences in xmitters/recvrs again. If you are running cables through walls repeaters can be problematic. They should be "in the middle".
Opportunity is missed by most people because it is dressed in overalls and looks like work. -- Thomas Alva Edison