The only OC on the I5-2500 is thru the increase in bus, and that is very limited (NOT worth it), and affect much more than the CPU causing problems. The k ver is OCed by raising the Multiplier (Deviation from previous Cpus where you could raise the bus and the Mulitplier.
4.2 is almost a given, with 4.6-> 4.8 not to difficault.
Took mine to 4.6 just by using ASrocks OC software (It's a little over aggressive on Vcore).
Bottom Line go for it - that is the K with a P67, or (I prefer) the Z68 MB.