The real world difference is negligible. The main difference is in the benchmarks. (e.g. 3d mark, WEI, etc.) You can go ahead and use 1600 memory. Lots of people buy it and run it at 1333 because they forget to turn on XMP mode in the BIOS. The price difference is like <$5, so it's up to you.
At the office I have 7 computers with the exact motherboard and CPU that you selected. I used Corsair XMS RAM from Amazon. They had 16GB for 70 bucks. Bought 2 kits and built 7 comps.
My personal comp uses DDR3 1866 RAM, but that's because I'm an enthusiast lol. My CPU runs at 4.5 GHz. With business boards, you likely won't be overclocking so it's best to just get the 1333 RAM and don't forget that SSD.
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