Sitting here bored at work, thought I'd just chat a little bit about the KVM setup.
It's a LASER brand KVM switch with PS/2 style connectors. Problem is that all my x86 retro boxes use AT keyboards and serial mice.
So, I made a bunch of custom pigtails to connect the AT sockets on the computers to the PS/2 sockets on the KVM switch, and another short adaptor to connect the AT keyboard. I could have bought adaptors, but the parts were actually cheaper.
The serial mice thing was a little more difficult, though. Since there was just no way to get the KVM to speak serial mouse language, I decided to build that part myself. I bought a 4-pole, 3-position rotary switch and some cable, found the four pins that serial mice actually use, and followed that through to the logical conclusion. It's not elegant, but it works fairly well, and even if I forget to toggle the switch before I power up a PC, I can just do it afterwards and re-load the mouse driver.