I7 960 vs i7 2600k

On a spec difference, the 2600k has a much higher OC capability, as the 960 does not have unlocked multiplier. It runs same power consumption, and i believe the same performance at stock, but the i7 2600k with an OC will smoke it.

They are both quad core with hyperthreading.
The 2600K is a 32nm(vs 45nm) part that has a higher(3.4 vs 3.2) clock rate.
The 2600K also has a more sophisticated architecture that will give it(10-15%) better performance per clock.
Lastly, the 2600K can usually be overclocked higher.

The main advantage the I7-960 has is that the X58 chipset it uses has more memory capacity and more pci-e lanes.

The upcoming sandy bridge-E will be better than either with 6 cores plus hyperthreading, a 32nm construction, and a much better memory and i/o capability.