http://www.newegg.com/Product/Product.aspx?Item=N82E16814102824
4850 512 MB
Of course it outperforms Xenos, look at any benchmark for multiplat games, it has higher details and higher resolution, and better frame rates. And the workup is in the anandtech article. You're not seriously going to argue that a 4850 is slower than the Xenos, are you?