When comparing Intel® Core™ i5-2500 and the Intel Core i5-2500K there are a couple simple differences.
Intel Core i5-2500K:
-Intel HD 3000 graphics
Intel Core i5-2500:
-Support for VT-d (directed I/O support)
-Support for TXT (Trusted Execution Technology)
-Intel HD 2000 graphics
-On average $15 less
For a business user the Intel Core i5-2500 is the clear processor for them due to support for TXT and the small cost savings. On the other hand for a person who is looking for the best processor value I would have to advise you to spend the extra $15 and pick up the Intel Core i5-2500K. On the Intel Core i5-2500K we have worked to make overclocking easier than ever before. So while you might not overclock it right now having that option allows you to extend the lifespan of the processor.
Intel Enthusiast Team