You can buy a better cpu with your budget. As the others have pointed out, most games don't use more than two cores.
$60 (after $10 MIR)
MSI mATX H55 motherboard + $111 i3-530
CPU. This is nearly equivalent to what you're spending for an AMD CPU/mobo on your budget.
The i3-530 blows away its competition (Athlon II X4 630) in
gaming performance. This benchmark is only at 1680x1050 resolution. It has exceptional overclocking potential in comparison (over 4GHz is normal using a stock cooler)
and still more efficient. Now, if you were doing something that utilizes more cores, going with AMD would make sense. We're just trying to help you get the best bang for your buck.