The problem with the III talking directly with Catalyst is that with the III the DP's do most of the actual DMX/ fixture control processing. This is so the console doesn't get bogged down with those remedial tasks

A DP-Artnet would be a great idea, would simplify things alot, but that's a good suggestion for High-End.

Using a GrandMa is great, I've done 5 servers off of it, and only simply hooked up a switch off the console and ran cat5 to each of the servers, made it very quick and clean.