mm if your comp has 4 slots for RAM then i think i would just get the extra stick of hyperX.I myself have the Gskill 8GB and love it but like i said if you have 4 slots i would just buy the extra stick. What ever is cheaper i would say unless you have money to waste.

Is your motherboard compatible with 1866? Make sure. Not all motherboards have that feature. Also, another thing, if you plan on just adding more memory rather than replacing it, make sure that you fill up all the slots rather than just buying an extra stick. An odd number of RAM chips can slash performance. And don't mix latencies. It'll also lower the performance to whatever the lowest latency is. So if you buy the 1866's and stick in a 1333 along for the ride, it will lower performance to 1333 making the higher latency RAM pointless. That's why they sell RAM in pairs, that's what the term 'dual channel' means and why the slots are color coded on your motherboard.