Core2 duo vs core2 quad

If you plan on overclocking the quad will match the dual at anything 3.4 Ghz+ and that is easy with the quad you picked out. This way you can get the same gaming performance and still have all the benefits of quads. If not, the dualcore will do better at stock, but not "way" better.

AT those speeds, the Quad will win in most anything. 400 MHz isn't that huge a diffrence, and the extra two cores will really show off at 2.8 GHz, even if you don't OC.