For any ram you are considering, do your own homework.
First, go to the motherboard web site and look for the QVL ram list. It is a list of tested and supported ram part#'s that have been verified to work with your motherboard. Other ram with the same characteristics should work also, but the motherboard vendor may give you a hard time if you use anything else.
As a second option, Go to the ram vendor's web site, and access their configurator.
Corsair, Kingston, Patriot, OCZ and others have them.
Their compatibility list is more current than the motherboard vendor's QVL lists which may not get updated after initial release.
Enter your mobo or PC, and get a list of compatible ram sticks.
Cpu performance is not very sensitive to ram speeds.
If you look at real application and game benchmarks(vs. synthetic tests),
you will see negligible difference in performance between the slowest DDR2 and the fastest DDR3 ram.
Perhaps 1-2%. Not worth it to me.
Don't pay extra for faster ram or better timings unless you are a maximum overclocker.