If you want to see how the GTX 460m ranks, you can click on the following link.http://www.notebookcheck.net/AMD-Radeon-HD-7570M.70631.0.html
Despite it's age, the GTX 460m is still considered a Class 1 graphic card for laptop. However, it is ranked at the bottom of Class 1 now. Included as part of the list are a few scatterings of desktop top graphic (black colored text). The GTX 460m is ranked below the Radeon HD 4850 and the nVidia GTS 450. The Radeon HD 6850 is ranked towards the top of the Class 1 list; top 25%.
For a single mobile graphic card solution you will need a GTX 675m to come pretty close to the Radeon HD 6870. Or the GT 675mx to get the same performance.