Futuremark released 3DMark Vantage on April 28, 2008. It is a benchmark based upon DirectX 10, and therefore will only run under Windows Vista (Service Pack 1 is stated as a requirement) and Windows 7.
It would be safe to say that you won't be running out of gaming performance with either of these configurations! With two GTX 580's in SLI, the overall score is 52,788 points. With two GTX 590's in Quad SLI the overall score is 63,497 points.