Sounds like you need a fiber backbone there. Cat5 will work for a good distance but the performance will degrade as you go farther and farther. You will have to go pretty far to have it just flat out not work. I made a 1000' patch cord out of a box of cable and just for an experiment used it from my PC to the wall jack and it worked. This is 1000' and approximately 190' of additional horizontal cable to the hub in the closet, it was pretty slow but it did work. Sounds like you need a fiber backbone there.
