"they make superb KVMs"
Do they?
I've just replaced my Belkin Dual Monitor KVM with an Aten. In all the years that I had the Belkin I had to have 3 keyboards, one for each machine, and one to stop the KVM from beeping to let me know there was no keyboard attached.
If I tried to use it with a single keyboard, 4 times out of 10, on switching machines, the keyboard would stop working. I tried with umpteesquillion different keyboards, and got no help from Belkin whatsoever.
The Aten cost one third the price of the Belkin and works perfectly.