Acer Aspire AM5100-EF9500A Information Needed

Hello,

I purchased an Acer Aspire AM5100-EF9500A Desktop PC

As far as I know, the above information is accurate.

MD Phenom Quad-Core 9500 2.2GHz
AMD 690G Chipset
3GB DDR2-667 SDRAM (Maximum Memory 8GB - DDR2-667/PC2 5300)
500GB Drive 7200 RPM
ATI Radeon X1250 (integrated)
Gigabyte Ethernet

I disable the onboard video card and purchased an ATI Radeon 8800GTS 320MB
but i find myself still getting video lag in my game. (World of Warcraft)

So im thinking of purchasing a new video card again. But I wanted to know if anyone has more information about what kind of motherboard Acer puts in these systems. Is it compatible with PCI Express 2.0? or do I need the old PCI express 1.X?

Thanks