Edit - I guess the other alternative is buy a better cpu cooler than my current one and see about overclocking at stock volts.
If budget is not a problem I would avoid this route. 4+ year pc life cycle being your "thing" the 2500k would be the right route to take, I would not even consider the 2120, for the reasons mentioned by Marine above.
(Recommended upgrade 2500k or Ivy bridge replacement)