By now, we're sure that you have heard and read many things about the lack of overclocking on Sandy Bridge processors. We have to agree that yes, the base clock is severely limited in terms of overclocking due to the fact that the base clock now governs everything on the platform. So you can't change it by much. No doubt, board manufacturers will continue to try to improve this aspect of Sandy Bridge, but our recommendation is to get a 'K' processor if you're really into overclocking.
After all, our best attempt at overclocking through the base clock yielded a mere 3MHz (from 100 to 103.5MHz), which gave us a total of around 4.1GHz. With an unlocked 'K' processor and simply by increasing the multiplier (air-cooled), we could hit up to 46x (from the base 33x or 3.3GHz). That's 4.6GHz during Turbo Boost and as you can see from our benchmarks, it's quite the increase. In Cinebench, the speed boost was able to help the Core i7-2600K beat Intel's mighty Core i7-980X in an area where it had such a tremendous advantage from its 6 cores.
The Core i5-2500K also managed a similar amount but obviously it did not benefit that much in Cinebench. We didn't see the overclocks doing too much in Far Cry 2, but you'll see the improvements in certain apps and software for sure.