Well, you'll need 2 3-port kvms with usb ports for mouse and keyboards for monitors 1 and 4. Computers 2 and 3 will need 3 video outputs(the easiest way to do this would be a 3 port vga or dvi splitter) and either 6 usb ports or 4 usb ports and 2 ps2 ports since both will end up with 3 keyboards and 3 mice. This setup will be a rats nest of cables, expensive, and a headache to setup but it's the only way i can think of to get the results you're looking for, have fun.
