What games do you [want to] play, and at what resolution? Maybe just a single GTX460 is enough. Do any of your games support PhysX? Have you chosen a PSU? A quality 550W unit can run any single GPU (450W for all but the very top end); you'll want 650W-850W for multiple GPUs. A quality PSU has full range active PFC (no little voltage switch) and 80+ certification for efficiency. Antec, Corsair, Seasonic, and Enermax are among the better brands.