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Buy the Q8200 and overclock it with a good aftermarket cooler. Best of both worlds then. High speed, and more cores ^^
Higher clocks is the way to go in most games. However, there are a few games (GTA4, ARMA2 spring to mind) that seriously benefit from having 3 or more cores, this is likely to become more prevalent in gaming, so having a triple/quad core is generally a better option if you want to play ALL games really well for a while to come.
However, the chips you picked are not the best choices for a gaming machine. First, the Q8200 is rather low clocked (2.33GHz) and doesn't overclock well, so it is not an ideal gaming chip and rather expensive (with a decent graphics card you will be CPU limited, which is bad). The E7500 is a better bet, but when you see triple and quad core AMD chips at the same price bracket, it isn't a particularly good deal. IMHO get an X3 720BE or the X4 630. Or if you feel the need to stick with intel, go the whole hog and get an i5 750 +p55 board.