well, tbh I upgraded to a i5 2500k from a i5 760 cause I was sceptical just like you. Surprisingly, I was actually right! A lot of people said there won't be any bottlenecks with my i5 760 but after upgrading, I started noticing a lot better gameplay. My gtx 670 gets at least 10+ more fps is battlefield3. Now that is an improvement. In general the fps is 5-10% higher in everything and gameplay is a lot more smoother and responsive too. With both cpus, my gpu usage was 99% with those games but the i5 2500k at 4.7ghz does a lot better than the i5 760 at 4ghz. The bottom line is, the sandy/ivy bridge would perform about 5-10% better than your current cpu, but is it worth upgrading the cpu/mobo just for that? well its totally up to you. Remember, the gtx 680 would perform about 2.5x the gtx 560, so your performance gain will be heaps. Maybe you don't even need that extra few fps. There will be some bottlenecks but you probably won't even notice it during regular gameplay.