Of those two. The M5A99FX Pro Rev 2.0 is the board you want. The EVO is just under the Pro without question really. They are nearly identical and both use a 6+2 VRM power phase. In fact the only differences between them are number of e-sata ports, sata ports, and pci-e slots.
The EVO has 2(x16 or dual x8), 1(X4mode,black) slots, and 2(x1), and finally 1 PCI slot
The PRO has 4(x16, x16, x4,x4), 1(x1), and finally 1 PCI slot.
Not much of a difference but with dual GPUs it could potentially be a little better. The PCI configuration of the Pro is more versatile as you can always stick a X4, X8, and X1 into a x16 slot but not the other way around.
Now if your budget allows the other choices to look at are the Asus Sabertooth, the Crosshair V or V Formula, Gigabyte 990FXA-UD7 or 990FXA- UD5. All of these have 8+2 VRM power phases and are great overclockers.