After reading up on temps, anything under 65C on TAT when under load is acceptable. While TAT was specifically developed for mobile CPU's, it also works correctly with desktop versions of C2D's, although the E4300 may be the exception (although these should still be pretty reliable)
As Clunk mentions, it's worth checking the application of thermal compound - I'm using an unlapped Tuniq Tower 120 and applied the AS5 thermal compound according to the AS guide. Compared to the stock Intel HSF, my temps lowered by at least 10C. However, due to my recent system problems I had to remove the Tuniq and found that there was too much TC for my liking. I'm sure with the correct amount I may have improved by up to 15C over the stock Intel HSF (so it's definitely worth checking).
For anyone that's interested, I'll be posting on my experiences of a noob bulding a new PC from bare components, including any wisdom gained from my selections and toils
