All of the processors that you've listed will perform/overclock very well (though make sure you have a good motherboard and power supply), the only big difference is what the stock speed is, and how high it has been binned.
When you're comparing processors in the same generation, the higher end models are usually the same processor that's been high binned (i.e. should perform better).
What you need to decide though is whether you want Ivy Bridge - E or Sandy Bridge - E. IB-E has PCI-e 3.0, whereas SB-E only has 2.0 (3.0 allows for more bandwidth). IB-E will also overclock less (when locking at clock speed) but will perform better per clock (4960x will perform better at 3.5GHz than a 3970x).
In the end, it's up to you, they are all great processors and will serve you quite well.