+1 on Crucial M4 and the i5 2500K
For you motherboard, consider the AsRock Extreme3 Gen3 or ASUS P8Z68-V/GEN3.
Get only 8GB of RAM. Anything more is a waste for gaming and could cause stability and voltage issues. Make sure it's low profile (even with the Noctua's adjustable high, they still won't have enough clearance).
If you will only OC to 4.0 to 4.5GHz, get a Corsair A70 or Hyper 212 EVO. Much cheaper and perform very well. You could probably push even further with those coolers, and the same for the Noctua.