My first wireless router was a Buffalo. I can still use it as a wireless router but can no longer flash the firmware. I'd love to be able to flash it with Tomato firmware, the router is on the list.  One of the nice features in the buffalo firmware is the ability to adjust the radio power.   You can set the signal strength so low it won't escape the room the router is in, only a wired connection is safer.  A nice feature of the router is the ability to add an external antenna.  Too bad Buffalo stopped making wireless routers for a few years.  On some routers flashed with tomato you are able to adjust the radio power.

It sounds like you have a nice setup.  I agree with your farm network setup observations.  Structures covered with steel, hills and trees cause issues for wifi networks.