Will it make a difference?
I used to work at a local computer store where they built office/gaming pcs all day and shipped them out. We would build 'gaming rigs' with Intel Extreme cpus that the client would never need, or 2xdual gpu sli, just ridiculously overpriced and overvalued parts. But for every single pc we built, we used the same 4GB sticks of 1333mhz black, low profile samsung RAM. I asked why we didnt offer the upgrade to 1600 to milk more money out of the rich clients, and the co-workers replied that "The only thing 1600 (or faster RAM) does is create problems." At that point, I already had 1600mhz RAM in my machine, and what do you know, a year later, my system wont run at that speed anymore.
That being said, if the choice comes up to grab faster memory at similar prices, go ahead and grab it. It will be most noticeable if you do photoshop/workstation stuff. If anything goes wrong you can always run it at 1333, just make sure you didnt pay an arm and a leg for faster speeds. Especially if you are building a gaming rig, just save money on ram and buy a better graphics card...