To be honest, there's a lot of hype over Ivy Bridge. Yeah it's slightly faster compared to Sandy Bridge at the same frequency, there's support for PCE3, but it's not up to the level where you'd notice significantly. If you can find the 3570k on sale, go for it, if not, go for the cheaper 2500k. It's getting real cheap these day.
For gaming, an overclocked 2500k is really good for the price. It's hard to beat it. Fish around for good deals.