there's 100mhz ontop on both turbo and base clock, for + ~15$.
performance gain is ~2-3%, so probably not needed.
talking about the 3xxx series, they're not any worse than 2xxx, they are bit better, just they are quite much hotter, and a bit more expensive, as expected of a new generation. also motherboard price will probably be higher because of the new chipsets. if you're fine with the pricing then you can go with Ivy Bridge.