Well it's got 4 pcie slots although they can be split, that can be troublesome. You'd have to use risers anways for decent gpus. But in any case, other than experimenting, you will lose money not make it with bitcoins. Even without paying for electricity, and running 24/7/365, you'd get maybe $1 in a year with 4 gpus. Gpus are just too weak comparatively. Ether or some other cryptocurrency would be a better choice but you are late and mining is getting harder and less profitable.