I am building a new computer and have obtained all of the parts except for the CPU. Some of these parts would work well with an i5 3750K, such as my ASrock Z77 Extreme6. Recently I have read a lot of things claiming that the new Ivy Bridge CPUs output a lot of heat when over locked. I intend to reach 4.5ghz and I have a Hyper 212+ with an extra pull fan. Can the i5 3750K overclock this high and still be stable? If not I probably will resort to the i5 2500K. What are your opinions? Thanks!
My advice to you: Z77 is optimized for Ivy Bridge, get an Ivy Bridge.
Its true that Ivy Bridge test samples are hot in comparison to Sandy Bridge chips. However, even with the limited information we have, 4.5Ghz is very obtainable/reasonable/stable/safe across all samples tested. All you'll need is a good air cooler.
Remember, Ivy Bridge isn't taking increased voltage very well, 1.3 is pushing the limit. Even the worst of the chip lottery will be able to get 4.5Ghz within that limit.
If you're concerned about longevity, Intel is offering a (one-time) replacement insurance for your chip, which gets added onto your standard warranty for a reasonable price: