You'll really not notice the difference running 2.5Ghz, except the temps will be noticeably higher because of the voltage.
Also, if I could suggest giving something a go:
C n Q. People bitch and moan about using it ith overclocking = death. It doesn't. If you're using the stock multiplier/voltage and just overclocking the FSB, then it can't do anything untoward. If you put in 1.4v, you probably couldn't use CnQ and benefit from some truly chilly temperatures.
Congratulations on the OC though :beer: