I have a core i3 540 non overclocked with 8GB of ram and a GTX 480 video card. I am considering buying a new motherboard, processor, and cooler and doing some overclocking. I would probably get either an i5 2500k or a 3570k. What I want to know is how much of a difference I would notice in my games.
First if your doing overclocking you shoud know that the Ivy Bridge cpu's are not very good at overclocking , they were made to be ow power alternative and when voltage is applied it tends to make them hot. You will be much better off with a 2500k for overclocking.
The single most important part in a gaming rig is the video card and the video card makes to biggest difference in game performance. If your current cpu was a bottleneck or he GTX 480 then going to the 2500k would get rid of that bottleneck. You will only see a performance increase in games that are cpu dependent like Arma and Civ 5.
I disgree, Ivy Bridge cpu's are good overclockers, they just run hotter, but they are also faster clock for clock and use less power, so a 4.2ghz Ivy is going to be as fast as a 4.5ghz Sandy. Even the Ivy non K's are good overclockers.