[Ailos]

About RAM speed and CAS latency: the latency is measured in cycles (e.g. 9-9-9-24 cycles). This also means that if you have a set of CAS 9 modules at DDR3-1333, (which runs at 566 MHz), sticking in a CAS 11 set at DDR3-1866 will actually decrease your latency. (9 cycles of 1.77e-9 seconds versus 11 cycles of 1.07e-9 seconds comes out to 15.93 for -1333 versus 11.77 for -1866). Moral of all this: don't be scared of the CAS numbers increasing for RAM modules rated for high speeds; remember they can always be turned down to run at slower speeds and slimmer cycle timings. Most modern motherboards, including the ones you're looking at, come with something called XMP profiling that automatically runs the memory at its fastest rated speed - just plug them in and everything's pretty much done by itself. Its possible to tweak the timings to be less generous than the automatic profile (and therefore, the latency be smaller), but you won't notice that much of a gain in any program even though you risk a lot of instability. If you plan to overclock, manually tweaking your timings will only make things that much more difficult for you, so I don't recommend doing anything about it until after you've finished tweaking the CPU.

But keep in mind that going from DDR3-1333 to DDR3-2133 will give you a very noticeably smother performance boost in PS2 - it did for me, and if you get a good deal on faster memory, I think it's money well spent. In any case, do not buy anything rated below DDR3-1600.

Asus, ASRock, MSI, Gigabyte are all good brands. I have personal experience with MSI and ASRock and found both to be reliable and decent overclocking platforms (I actually have the Extreme 4 you linked). In your shoes, I picked the ASRock simply because it was all black. (Both the MSI and ASRock come with 8 GB of memory, btw.)