I'm not a network expert by any means so this is a question from ignorance that may be met with a swift "no". Would it be possible to use something other than CAT5 to connect a Mac to a PC? firewire possibly? That would really simplify our connecting to the internet and internal network. If not, what are your all's setups like in this regard?
You can connect as simply as WiFi but the playback will be less smooth, while we're not sending a lot of data in terms of size between the two systems, the time data is a continuous stream that if interrupted results in the player being 'jumpy'.
If you have a method for using firewire as a network port on your PC then it's entirely possible that would work for connecting between the two, just set up a Firewire network device in your Network Preferences in the MacOS.
Personally, when I go to studios to do demos etc I take an old Apple Airport Extreme to connect the Mac and PC to, if they had an uplink in the WAN connection port of that device then both systems would also gain internet access via the Airport Extreme assigned IP addresses that you'd be using to connect PC Player to Mac Renderer.
Hope this helps, if you can give me more information on your setup maybe I could come up with other plans for you too.