| posts: 35 | Location: Newbury, UK.
I use 'HDMI Ethernet Baluns' at work to manage connections between an HDMI matrix and four Epson HD projectors. The baluns work great and retain the original HD video source quality. I use CAT6, but there is no reason not to use CAT5e. Distance before degradation is about 40m in my experience, but the specs usually say 50m.
Each Balun is powered, so take that into consideration, and some models also support IR modules/probes so you can control them remotely, if you have the baluns stashed in a floor or ceiling void.
Google Neet Cables HDMI Extender Baluns. About £40 a pair on Amazon.