In answer to the question about video (or computer output) to Cat 5 (or Cat 6), one of the best is made by Magenta Research
http://www.magenta-research.com/cat5...ansmitters.htm
You will need to do some research to find exactly the right box to fill your application(s).
These are comprised of a transmitter on one end and a receiver on the other. Depending on which transmitter you select, to you can send composite, s-video, even HDTV as well as computer generated graphics down standard Cat 5 or Cat 6 line with virtually no loss. Each box requires local power (wall wart). Lead length can go into miles or certainly within the confines of any church or venue I've used. Another feature that's in the plus column, there is no cross talk between such as nearby power cables. You can use these "boxes" also to feed projectors. They have audio as well as video. Bottom line, they aren't cheap, but they will knock your socks off.
Best Rgds,
Ed