Those speed won't make too much difference. Get 1866 if the prices are matching or not more than $5 difference with 1600. Make sure they have better Case Latency(CL) like CL9 would be the last you should be expecting(Lower the CL better the performance you get CL9<CL8<CL7; so CL7 would be the best for you). Get 16gb if you are really up to some heavy multitasking.
In gaming the CPUs are pretty much a tossup, though the Intel is stronger, but when you consider the design, rendering, editing, the definitely go the 4770K, much stronger and faster....say this because it also affects the DRAM - with 8350 the 1866 is about the tops you can go, where the 4770K can run about anything up through 2800+ in DRAM and Haswell likes fast DRAM....I'd suggest 16GB in a 2x8GB config based on the variety of design work shown in 1866 or 2133 (and possibly higher), would look at the GSkill Tridents or Snipers for the DRAM 1866/8 or 9 or 2133/9