I have a 50 ft HDMI cable run where I run 1080p to a Pearl projector, and I have had no problems whatsoever. I also purchased the cable from Monoprice, it was their highest quality, thickest gauge 50 ft. cable, but it was still less than $100, which is an amazing value.
I will say, however, that I run the HDMI cable into an HDMI switcher, and I believe the switcher may have an integrated signal booster or equalizer.
I would buy the thickest monoprice one possible, you should be fine with 50 ft, even without a booster. Their cables are definitely high quality, and with a digital signal, I have a hard time believing you get any performance advantage whatsoever from a more expensive cable, it either works or it doesn't.
It is criminal what companies like Monster charge for HDMI cable, I have had many clueless friends drop $100 at Best Buy for a 6 ft cable.