The minimum requirement is always exaggerated to account for crappy PSUs. Even with a 9600GT your system probably wouldn't use more than 200W while gaming or benching, though you may pass that if you run fur mark and prim 95 on what would otherwise be idle cores.
Anyway if your PSU has enough amps on the 12v rail then you should be fine. Personally I would say get a high quality PSU if you can. A 450W Antec, Corsair, or FSP should do just fine.