I use IOGEAR
http://www.iogear.com/main.phphttp://www.iogear.com/main.php?loc=product&Item=GCS712U&name=MiniView™%20Micro%20USB%20Audio%20KVM%20Switch
I have 2 PC + A4000 hooked up to it. It is PS2 connections for keyboard and mouse. I use 1 monitor, 1 keyboard 1 pc mouse and the amiga mouse for the amiga plugged in the amiga. Works great for me. To switch from the monitor,keyboard and mouse for the PC I use the "scrool key" on the keyboard. The main monitor plug is connected to a switcher box so when I use the amiga, I use the switcher box. Hope this makes sence.
cheers