New PC Built. NEED ADVISE!

Is this system built good? For pure gaming performance. If not, which part do you suggest to have better/smoother gaming performance? Thanks a lot! AMD PHENOM II X4 920 HDX920XCGI CPU BOX MAGIC PRO MP-AKGX EXTREME GTS/AM2+ AMD790GX M/B Kingston Hyper-X DDR-2 800MHz 4G (2Gx2, CL5) OCZ StealthXStream 600W ATX12V 20/24PIN Active PFC ATX Power Supply 120MM Fan Black LG GH-22NS30 22X SMulti DVD Writer SATA/Black Sapphire藍寶石 HD4870 PCI-E 1GB DDR5 COOLER MASTER CA-RC334KK Elite 333 ATX Case/Black Cooler Master CF-R4S12AK 12CM Case Fan Cooler Master RR-CCH-P912-GP Vortex 752 Cooling Fan

Is this system built good? For pure gaming performance. If not, which part do you suggest to have better/smoother gaming performance? Thanks a lot!

AMD PHENOM II X4 920 HDX920XCGI CPU BOX
MAGIC PRO MP-AKGX EXTREME GTS/AM2+ AMD790GX M/B
Kingston Hyper-X DDR-2 800MHz 4G (2Gx2, CL5)
OCZ StealthXStream 600W ATX12V 20/24PIN Active PFC ATX Power Supply 120MM Fan Black
LG GH-22NS30 22X SMulti DVD Writer SATA/Black
Sapphire藍寶石 HD4870 PCI-E 1GB DDR5
COOLER MASTER CA-RC334KK Elite 333 ATX Case/Black
Cooler Master CF-R4S12AK 12CM Case Fan
Cooler Master RR-CCH-P912-GP Vortex 752 Cooling Fan

Since no one has replied I will offer my advice.

First off what is your budget?

Second I would go with an Intel CPU and go with a DDR3 mobo.

Third I would use an nVIDIA graphics card.

Before we can get too detailed the budget is a main parameter.