i built something like this a while back just not quite as grand lol
instead of trying to wire all 3 to one psu reuse the power bricks from the ps3 and xbox and just combine the power cables after the bricks and psu it will save you some wiring. You can actually wire the monitor cable directly to the xbox 360 power brick once you disassemble it.
also how do you plan on switching video between systems? Will you be running any sort of extensions on pieces for the usb headers? are you going to have just one power button or 3 separate ones
one last thing, I hope you realize the shear amount of custom wiring and custom parts that will be involved in this build, if i remember correctly some of the connectors for the hdd and cd drive on the xbox are not standard cables and are extremely short and will need to be cut and lengthened
Not trying to deter you I really enjoyed building mine just dont want you to tear down over 1k of products and have a problem Edited by racer86 - 1/17/13 at 9:13pm