• 1 x PCIe 3.0 x16 slot (PCI_E2, supports x16 speed)
• 1 x PCIe 2.0 x16 slot (PCI_E4, supports x4 speed)*
• 2 x PCIe 2.0 x1 slots
• 3 x PCI slots
* The PCIe x1 slots (PCI_E1, PCI_E3) will be unavailable when installing an expansion card in the PCI_E4 slot.
This means your 2nd video card will have 1/8 of the bandwidth of the first one. PCIe 2.0 running at x4 is not enough for high-end gaming cards. Minimum of x8 speed is recommended. I don't think this motherboard will provide good results with CrossFire. If you would like to stick to MSI - get the MSI Z97 Gaming 5 - it has 2 slots running at x8 speed.
Also, instead of the 4770k - get a 4790k. It is the same price, but 500 MHz more.