I just double checked, and there is a 2nd Crucial memory Kit of 8Gb as well.
(When I first did it, I did not notice the option to click and see ALL compatible devices, there were a few others as well, but they were all less than 8Gbs, so I left them out of this quote).
Presumably the fastest (1600) one at the top, as in my original post, is probably the best to go for, as if you put it into another computer later, it is a faster 1600, rather than the slower 1333 (although the CAS latency changes as well).