I just upgraded my secondary box from a A64 2800 to an A64 3400, a 33% increase in clock speed (from 1.8 Ghz to 2.4 Ghz), the only thing I changed was that I used Arctic Silver 5 as the thermal grease instead of the stock heatsink pad. My full load temp dropped from 52C to 47C...after a 33% increase of clock speed...holy crap is that stuff good.