http://www23.tomshardware.com/cpu_2007.html
Note that these tests are done on non-overclocked CPUs. Estimating overclock performance is not an exact science but the best thing to do is look at the chip with the most similar model number at the speed you're looking for. E.g., if you're going to get a Q6600 and overclock it to 3GHz, it will be roughly as fast as a Q6850.
Also see the "more charts" box at the top for video cards.
--------------
Edit:
Newer version of the chart:
http://www.tomshardware.com/charts/d...se-10,835.html