The easy way to upgrade a system is to throw as much money as you can manage into the system in the hopes of overcoming bottlenecks.  This is not the most efficient way, but if all you are a power at any cost type of enthusiast it can certainly work.  Others are more concerned about performance per dollar, and that is when scaling reviews like this one at [H]ard|OCP come in very handy.  They’ve taken a Core i7 920, a QX9650, and AMD’s Phenom II X4 810 & and X3 720 BE, overclocked them all to 3.6GHz and set them against 7 popular games.  See how they perform in the games and how they compare price wise in the full review.
“Four processors; Intel Core i7 920, Intel Core 2 QX9650, AMD Phenom II X4 810, & AMD Phenom II X3 720 BE. Seven games. REAL WORLD GAMEPLAY at stock clocks and all overclocked to 3.6GHz, head to head, & apples to apples.”

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