I have no idea about that motherboard, but you've chosen the best model of CPU in my opinion. The E8500, and E8600 are of course better, but also more expensive so it depends on you budget.
Duo cores are better then quad cores for gaming, because almost no games are written to take advantage of all 4 cores. so you'll get better bang for you buck paying for only 2 cores.
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I have no idea about that motherboard, but you've chosen the best model of CPU in my opinion. The E8500, and E8600 are of course better, but also more expensive so it depends on you budget.
Duo cores are better then quad cores for gaming, because almost no games are written to take advantage of all 4 cores. so you'll get better bang for you buck paying for only 2 cores.