What power supply do you have in your computer? We need to know that before we could advise what to upgrade, in case your power supply can't power an upgraded power hungry CPU or graphics card.
Please note your motherboard does not support the Phenom II X6 CPUs as its power circuitry is weak, the higher-end X4 CPUs will also push the board's capabilities, although they are supported.
As above, the CPU and graphics card both need upgrading in order to play modern games, you could also do with an additional 2GB+ of RAM.