Graphic Card Choice(gpu),Power Supply Question.?

Hi My pc specs are AMD 6300 3.5ghz 4gb ddr3 1333mhz and a vga i wanted to buy Sadly for me, i dont have much money to spend. Plz tell me if 1 of the following cards can keep me playing the new games ( not max graphics ofc) for 1- 1+1/2 years hd 7700 1gb gddr5 gtx 650 1gb gddr5 (this is just a short question, if not its ok) the main question is this; i got a 500w power supplier. If i buy a new vga, will it work? or there will be a messup with the connections and the wires etc? . i think it was not expensive,and i cant afford a new power supplier too sry for bad english, did it rushly