The best way to measure performance is by using real programs. The problem, though, is creating a methodology using real software that provides accurate results. For Photoshop CS4, there is a methodology created by the folks at GamingHeaven that is very accurate. Their script applies a series of 15 filters to a sample image, and we wrote down the time taken for each filter to run. At the end, we have the results for each individual filter and we simply added them up to have the total time taken to run the 15 filters from the GamingHeaven batch. The results below are given in seconds, so the lower the number the better.
On Photoshop CS4, the Core i5-2500K (3.30 GHz) was 19% faster than the Core i5-661 (3.33 GHz), 36% faster than the Phenom II X4 975 (3.6 GHz), and 44% faster than the Phenom II X4 970 (3.5 GHz).