How much are you willing to spend? For me, I recommend a card by nvidia simply because they perform better in games then the ati compartment. so dont be fooled that ati cards have the better specs for a more decent price

If u have a good power supply and $230, heres a 8800GT 512MB. Out of all the video cards, the 8800GT is the best deal due to its specs and price ratio - Newegg.com - EVGA 512-P3-N801-AR GeForce 8800GT 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card - Retail

Decent power supply and $180 - 9600GT 512MB (offers close to GT performance) Newegg.com - EVGA 512-P3-N862-AR Superclocked GeForce 9600GT Superclocked 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card - Retail

$300 and good power supply (offers close to 8800GTX specs) - 8800GTS 512MB Newegg.com - EVGA 512-P3-N841-AR GeForce 8800GTS (G92) 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card - Retail

$410 top of the line - 8800GTX 768 MB Newegg.com - EVGA 768-P2-N831-AR GeForce 8800GTX 768MB 384-bit GDDR3 PCI Express x16 HDCP Ready SLI Supported Video Card - Retail

Budget $100 Video Card, 8600GT 256 MB (midrange card) Newegg.com - XFX PVT84JUDD3 GeForce 8600GT XXX 256MB 128-bit GDDR3 PCI Express x16 SLI Supported Video Card - Retail

I can tell you that I have a 8600GT (not the one I posted, a slightly weaker one) and it can play wow on high settings, cod4 on high setings, cs:s and hl2 on max settings.