The nVidia GT 645m is more powerful than the Radeon HD 7660g + Radeon HD 7670m.
http://www.notebookcheck.net/AMD-Radeon-HD-7660G-HD-7670M-Dual-Graphics.81173.0.html
Using the AMD Radeon HD 7660G + HD 7670M Dual Graphics as the baseline....
-Crysis 3 (Low Settings): GT 645m has 48% better performance.
-Dead Space 3 (High Settings): GT 645m has 47% better performance.
-F1 2012 (Ultra Settings): GT 645m has 87% better performance (the GT 645m is only listed as part of the Ultra settings)
-Torchlight (Ultra Settings): GT 645m is not listed, but the slower GT 640m has 80% better performance.
-Sleeping Dogs (Low Settings): GT 645m is not listed, but the slower GT 640m has 54% better performance.
-Risen 2 (Low Settings): GT 645m is not listed, but the slower GT 640LE (slower than the GT 640m) has 30% better performance.
-Anno 2027 (High Settings): GT 645m is not listed, but the slower GT 640m has 16% better performance.
-Skyrim (High Settings): GT 645m is not listed, but the slower GT 635m has 18% better performance.
-Battlefield 3 (High Settings): GT 645m has 8% better performance
-F1 2011 (High Settings): GT 645m is not listed, but the slower GT 630m has 43% better performance.
-Deus Ex: Human Revolution (High Settings): GT 645m is not listed, but the slower GT 640m has 7% better performance and the faster GT 650m has 37% better performance.
-Dirt 3 (High Settings): GT 645m is not listed, but the slower GT 640m has 45% better performance.
-Mafia 2 (High Settings): GT 645m is not listed, but the slower GT 630m is equal to the Radeon Dual Graphics combo.
-StarCraft 2 (Ultra Settings): GT 645m is not listed, but the slower GT 640LE has 30% better performance.
-Trackmania Nations Forever (High Settings): GT 645m is not listed, but the slower GT 640m has 57% better performance.