It should work well though a bit overkill for gaming in terms of cores, a bit lacking in gaming in speed. As core counts increase the clock speed decreases with intel cpu's. One of the main perks with the 5960x is the pcie lanes, there are 40 so enough to run both cards at x16. There's only a slight improvement over x16/x8 though on a cpu with fewer lanes.
The 5960x out of the box is clocked at 3ghz with turbo up to 3.5ghz. Compared to an i7 6700k which only has 4 cores with hyperthreading but has clock speeds of 4ghz and turbo up to 4.2ghz. In some games the 6700k will outperform the 5960x based on clock speed. Hyperthreading doesn't really have a lot to do with sli by itself. Also not all games support sli, but that's another...