Does anyone know if these can handle demanding games?

Check this video out he shows off the specs/overclocking and benchmarks

I read online that gpu power is same as A5800k, and it is very good with dedicated gpu with 2133Mhz RAM, it is quite fast as quadcore and you can overclock it good. Linus showed the new Mobo from gigabyte (fm2) which overclocked 6800k to 6.7 or something Ghz with liquid Nitrogen

That's their top-end desktop model. Basically, it'll play almost any game out there at 1080p or 720p, but on low-ish settings. It'll work, but it's obviously not up to the level of a dedicated card.