I have the third one which has worked well so far. In general, I'm a big fan of G.Skill so any of those will probably do. Make sure to look through the reviews for possible incompatibilities with your motherboard. To answer your question though, as long as you set your ratio 1:1 you could even use 800Mhz RAM. Having 1066Mhz gives you a little flexibility in your overclock if you choose to go over 400Mhz on the bus.