Yes. It does matter. What graphics card should you get without knowing the system requirements? That depends on the resolution you want to game at.
I would recommend at least the nVidia GT 635m for 1366x768 resolution, at least a GT 640m (not the 640m LE) for 1600x900 and at least a GT 660m for 1920x1080. The more performance you want, the more powerful graphic card you should get.