Why would you ever get 2 year old tech when you could get either the newest thing which is Haswell or at least a 3570k which is the newest thing out right now? THe 3570k performs about 8-10% better all around than the 2500k. And for only 3% more of the price. Which is like 10 bucks.
I agree with ericjohn in that the Intel® Core™ i5-3570K is the way to go. Due to improvements in the IPC of the 3rd generation Intel Core processors it doesnt matter if you can overclock it as high as you can the Intel Core i5-2500K in the end you get a processor that will performnance as well in performance.