Could anyone recommend a reliable Brand of KVM Switch for a 4 PC render farm?     It needs to be USB, DVI Based.

Maybe this will help. Just follow the link. As to the DVI you can use a VGA to DVI adapter.

http://www.newegg.com/Special/ShellShocker.aspx?nm_mc=EMC-SD082011&cm_mmc=EMC-SD082011--SD081511--item-_-singleitem

I've been using "StarTech" brand for a 2 way KVM VGA and am highly satisfied with it.  I run 2 Dell 27" monitors with 2 main PCs.  VGA works fine to the 1440x1200 Monitor limit.  With DVI you can get higher resolution per monitor.  I've had that KVM for the last 6 years

I've been looking at acquiring a 4 way KVM with DVI-USB as well for the same purpose and the StarTech will be my first choice. 

Note that as soon as you introduce VGA into the cabling you will be reducing the resolution of the monitors, as VGA has lower limits in spite of the DVI-VGA convertors.

I've had StarTech, for a long haul connection (noisy machines upstairs, monitor etc in the living room, very quiet). Some problems (mouse incidentely going nuts) can arise when different pieces of the setup are on different power groups in your house.

I had a 4-PC renderfarm a few years ago, but preferred to control it over the internal LAN using the build in Windows Remote Desktop facility. One box controls all, the other boxes only need a Start button, once setup properly. No hardware attached.

Have fun

Thanks every one for your interest and replies.

I've settled on a KVMP recommended by Pamela Case (Forester) and bought a IOGear; it has a dual link and twin view connection. Yes it was VERY expensive AU $720-. For me it was well worth it. I had burnt out one Belkin KVM and two Lindy KVM's. I worked out that they just couldn't cope with a powered USB Hub on the peripherals Port.

The USB hub is very important for me as I can plug in an external HDD, handy for transferring files and applications between computers.

I started with inexpensive KVM's which had  VGA connections. First problem was that the colours didn't come out right and as was already said, I had problems with the monitor resolutions.

I just got the IOGear KVMP today and am very happy with it.  :-))

Thanks again every one.