FYI.. you only need 3+ GHz on cpuNB speed if you are running 2000+MHz ram.
Rule is 3 times ram speed (2000 = 1000MHz)
However faster cpuNB can help in 2D tasks the difference is pretty minimal. For benching I increase it (hey if it is an extra couple seconds in 32M I am in

) but for general overclocking not necessary.