I saw that, but note it's 2.66 GHz vs 3.33 GHz, so it isn't clear to me that it is better/faster for what I do/the software I use.
Basically the central processor chip can now have multiple processors cores built into the silicon chip (a core is effectively another processor core, i.e the original Pentium 4 etc just had 1 processor core) so although the Q8200 runs at a slower speed it has 4 processors compared to the E7500s 2 processor cores.
4 x 2.66 Ghz (10.64) is > 2 x 2.80 GHz (5.60) so roughly around 80% faster
This is better for a multi-threaded operating system such as Windows XP and Vista. (if using the PC for video work, one of the cores would work uninterrupted carrying out video rendering, whilst you work on a spreadsheet for example)
An analogy would be comparing a slightly slower 4 cylinder auto engine to a slighty faster 2 cylinder; i.e. more power and smoother operation.
Edit - updated the processor speeds for the E7500 which runs @ 2.8Ghz