With a full tower like that board size won't be an issue. Then you just have to decide on A) budget for the build B)How many PCIE slots do you plan to fill with graphics cards, now and in the future. For a good build with good utility and cost sense, the Sabertooth X79 will be good. If you're planning on filling that tower with power something like the Asus Rampage IV Extreme would be awesome. Not only will you fill your case with a good looking board with a lot of amenities, but you'll have all the slots and spacing you need to maximize GPU connectivity.
If you don't plan on doing more than 2XSLI, than the Sabertooth is probably your good bet. If money is no object and a truly enthusiast build is you goal, that Rampage IV is a...