Re: ASUS P5QPL-AM video card options
it's PCIe x16 compatible. Basically all that is going to matter with compatibility is its size (whether it fits in the case) and whether the drivers support your OS
the Sapphire or ASUS models of the Radeon 1GB cards are all pretty nice.
i personally recommend the Sapphire 5770/5850 etc.
(apologies if im wildly out of your price range, not sure of US prices on this stuff)
EVGA SLI Micro Z68 // Intel i5-2500k // 8GB Corsair Vengeance 1866MHz // Overclocked 2GB MSI R9 270X // Corsair Carbide SPEC-03 // Kingston Hyper-X 120GB // 2TB WD Green + 500GB WD Black