Since SLI or CrossFire isn't supported with your motherboard you won't need a power supply that handles any more than one high end discrete graphics card.
Choose a name brand such as Antec, Corsair, Enermax, PC Power & Cooling Silencer Series, Seasonic, XFX.
A name brand 600 Watt power supply unit should be able to handle any of the single highest end discrete graphics card on the market today.