Can it work on psu 500w
You don't have anything very demanding, a 300W would likely work. But if you are buying anyway, might as well go ahead and get something better. What brand was you looking at getting? The guys here can help with selecting a good brand.
Im going tu buy a neew grafic card
GeForce GTX 660 it needs a minimum of 450w
So can I by a 500w psu four this matherbord
Yeah, as long as the power supply will deliver the required power. It would be over-kill but you can get 1200W if that is what you wanted.