custom case dimensions need a little info

[terramir]

thinking about building a new case from scratch with two sides freezone chiller with additional radiator and 3 fans on one side, mobo drives on the other. the whole thing a bit of industrial art. The thing is I would like this to be just big enough to suit any motherboard imaginable, I.e. if the bug bites me and I decide to make this a 24 core monster (i.e. 4 processor i7 server board ala crazy) then I want to be able to do it. so I need to know the following things the max length of usual motherboards is about 30.5 cm about 12 and well I've not seen boards much bigger than 8 1/2 inches wide but then again I know they exist. what are the biggest form factors there are so I can future proof my case. Also add on cards what are the longest ones you could imagine. I'm in a serious planning stage here right now I'm thinking 40 cm i.e. 16 inch cube but I might go bigger if you guys show me boards that are much bigger than that.
terramir

[terramir]

EVGA's SR-2 motherboard is 15 x 13.6 inches. yes and I've seen 4 processor opteron boards at 16.2 inches x 13 inches but as of yet can I find any quad processor intel boards many max of 48 virtual threads holy cow that would be nuts. anyways at first I was planning a 40 cm cube but now I'm opting for 45 cm which amounts to 17.71 inches that should be future proof enough.we'll see how it turns out.
terramir