The 9XXX Volcanic Islands series of AMD GPUs will be on the 20nm architecture. Since the 9970 may use less power to run games, it's ideal to buy a 650W PSU. Make sure it's a brand that is trustable e.g. Seasonic, Sirtec / High Power, XFX, Antec, Corsair etc. Some brands are recognisable but make terrible PSUs e.g. Aerocool, Akasa, Cooler Master (GX, GX lite, B series, elite). Choose wisely for your soon-to-be-new GPU.