I am going to purchase an i5-3750k to go with my new build when ivy bridge is released. How do voltages tie into overclocking this processor (since it hasn't been released lets just use the 2500k as a reference)? Is it enough to just increase the multiplier until I get my highest stable clock (hopefully 4.5ghz) and not alter the VCore? If not, what is better? Increasing or decreasing VCore? From what I understand, increasing VCore will raise temps and can shorten CPU life, but is there any benefit in stability (assuming adequate cooling of course). Another possibility that has crossed my mind is that I should raise my multiplier until I can't go higher, and then decrease voltage until i reach my lowest stable voltage. I have never overclocked before and I am just trying to make sense of it all. Are there any other voltage settings that should be adjusted? Thanks!
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-bridg...
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.
With adequate cooling, increasing VCore will typically give you more headroom for overclocking, at the expense of higher temperatures which can potentially shorten the lifespan of your CPU. Anandtech has a good article which goes into Ivy Bridge temperatures and max stable frequency versus voltage, as well as temperature vs frequency.