Any major brand (Corsair, OCZ, G.Skill, Mushkin), and look for a set rated for 1600Mhz.
That will take you pretty much anywhere you need while overclocking your processor, and still leave plenty of headroom.
And between sets with much higher prices for things like slightly tighter timings (for example, 8-8-8-24 vs. 7-7-7-20), save your money and go with the cheaper set. Performance differences are minuscule.
Whatever you want. The IMC, or Integrated Memory Controller, is on your chip, and this is the most important part as far as memory. The IMC is like the rest of the chip, in that there is some variance between chips. In all likelihood, it is similar to most chips' IMCs, 4 GHz QPI (AKA 8 GT/s QPI), will never be made stable with OC'd core clocks, if at all; this is what you would get running RAM at 2000 MHz. Therefore, if you want to OC with 2000 MHz RAM, you will just end up setting it at 1600 or 1700 MHz, but with tighter timings. What I am getting at, is that sn0man is entirely correct (for several reasons), when he says "look for a 1600 MHz kit".
A forum community dedicated to overclocking enthusiasts and testing the limits of computing. Come join the discussion about computing, builds, collections, displays, models, styles, scales, specifications, reviews, accessories, classifieds, and more!