I really like the Xbox dems., maybe make it 3.5 inches tall for moer PSU room... FlexATX seems a good size, you can get 500 watt ones, put a reg. height GPU in with a riser, a 3.5 cutout for those 3.5 i/o panels you can buy so get a MB with certain i/os just get a panel with those & like 2 3.5 internal drives... I have it all in my head, but no idea on how to build it in a CAD program...