Should I buy a gaming computer with One nVidia GTX580 1536MB GDDR5 RAM PCI-E or Two XFX Radeon HD 6950?

The two XFX Radeon HD 6950 2GB GDDR5 will be set in crossfire...|||The amd 6950 crossfire would increase your fps while gaming even Bf3 would play at ultra setting with no problems , a gtx 580 would handle all games at high settings with the right specs, if not on a budget then go for the amd hd 6950 crossfire there isn't a game on the market today that those two cards can't handle again with the right specs.|||Definitely the Radeons, not because of more memory like that other boob said. At this point it won't make a difference. The two 6950s combined are simply faster than a single GTX 580.|||Radeon- More memory