your2sorry

I have a Intel Core 2 Quad Core Q6600 2.40GHz PC with a ATI Redeon 5670 HD. It plays most games on high settings but a lot of the current games only run on medium settings. I would like to build a new rig but money is tight. Can I get away with just upgrading the graphics card? I was considering a gtx 670. Would just upgrading the graphics card fix my issue? I would like to play most if not all games out right now on max settings. Is my computer even capable of handling such card? Any advise would help thanks.