I've got a 2500K system that will ruin most i7's.
Thats less likely these days, I thought the same when I had mine, but after investigation I found that the minute increases in performance have stacked up quite significantly, so to match a current stock i5 7600K or whatever it is called you'd need to be running over 5GHz, and that would only match an i7 in applications/games which don't use more than 4 threads.
2500K is still an excellent chip though, I'd still be using mine were it not for the fact that a 2700K came up very cheaply.

Certainly no plans to upgrade from Sandybridge just yet! We definitely bought at the right time.