Since you are overclocking, do not go with the i5-3570K unless you are packing some serious cooling. Ivybridge runs notoriously hot compared to sandybridge. In order to achieve a high overclock, you will need to raise the vcore. However, a voltage being raised will not damage the processor unless you are going above specified voltages for the processor. Besides voltages, there also are wattage and many other power options. Read this for an example: http://www.tomshardware.com/forum/274821-29-sandy-bridge-series-overclocking-cores-guide
There are also temperatures to deal with, and too high temperatures can damage your processor. Plus, you won't be able to raise your multiplier that high. The processor or board will cut you off, plus you will need an insane amount of vcore and cooling.
What is your budget for cooling? I seriously would go with the core i5-2500k for overclocking.