If, like you said, you don't overclock and never intend to, the i7-2600 will be faster than the i5-2500K.
The i7-2600 has Hyper-Threading which can give a significant boost in well threaded workloads (heavy multi-tasking, video encoding, 3D rendering etc). It also has a 100MHz higher base clock which should result at +100MHz at 1,2,3 and 4 core loads. There's also the matter of the 8MB vs 6MB L3 cache - although the extra overhead of Hyper-Threading may make the extra cache necessary to avoid L3 thrashing, rather than an explicit benefit of +2MB L3.