The typical size of an ATX motherboard is about 9.6" x 12". EATX: 13" x 12" -- A fully-featured ATX motherboard with an extended width of 13" and height of 12" instead of ATX's maximum of 12" x 9. ...
BRIONY gets a look at a new case from ASUS - the TUF GT501 Chassis - its a monster case, and priced around £150 in the UK.