You can see below just how small a gap, in performance terms, there is between the i7 3960X and the i7 3930K.

It's also interesting just how close the latest traditional Sandy Bridge chip, the Intel Core i7 2700K, is in general performance terms too, especially in gaming and single-threaded speeds.

3D rendering performance

Intel core i7 3930k

Intel core i7 3930k

Video encoding performance

Intel core i7 3930k

CPU gaming performance

Intel core i7 3930k