To play the devil's advocate (advocating evil Intel), I can't help but point out that the i5-2500 pretty much out performs the poor AMD X6 1100T in almost every benchmark you can think of, and most real word situations at stock speeds, while offering superior overclocking headroom.
Edit: I just took a peak at Anandtech's bench page, and the i5-2500k dominated every image processing application listed.... including 3dsmax, Blender, and Photoshop.
Second edit: If price is a concern, I'd probably stay at an i5-2500k vs a 2600k, since the performance difference is usually pretty minimal in most applications. Depending on the image processing software you use, you might not notice the difference. The AMD processor, however, just doesn't seem to perform well enough to justify for your desired task, unless you have a strong personal bias against Intel, and would rather use an inferior product than give Intel money.
I'd understand if that's your stance, since some people take serious issue with Intel's history of monopolistic practices... but the unfortunate truth is that AMD cannot compete with Sandy Bridge.