If you still need it and for anyone out there wondering how to hook up an M.2 SSD to the VIII Impact:
http://www.microsatacables.com/m2-to-u2-sff8639-pcie-x4-gen-3-adapter-sff-937-4xgen3
It's possible - you need an adapter like the one above. M.2 SSD goes into the adapter, the adapter connects to the motherboard via the U.2 port, and the whole thing is mounted as a regulat 2.5" drive. A side benefit of this setup is that you provide better cooling for the M.2 SSD and keep heat away from the motherboard. That's also the reason Asus gave for not including an M.2 slot on the bottom of the VIII Impact - heat. Still, it begs the question why didn't they put the M.2 vertically next to the sound board, for example; or why they chose not to include the necessary adapter with such an expensive motherboard. But there you have it. There is a way. Maybe the next wave of consumer PCIe SSDs would be predominantly U.2 and 2.5", and Asus know this. Maybe not. Waiting might be a good idea; as is getting an Intel 750.