naa, hsf won't change it, it'll keep it cool though, also.. you may wanna start looking into changing the voltage on the chip.. if it's not getting enough power it'll lag out and not use it's full setting =) risky risky...
i'm keeping my 2500 at o/c at 1.9 right now, i just changed the fsb to 400 and uped it a few mhz, stable at 50c with stock hsf, check out the slk-900 i think, also i heard the tornado fan would work well witht that heatsink, although loud, i think you could get that 2500 to a possible 2.4g (with correct settings)@50c-55c wow!