These are the official recommended power requirements based on your graphics card:
450 Watt or greater power supply with one 75W 6-pin PCI Express® power connectors recommended (600 Watt and two 6-pin connectors for ATI CrossFireX™ technology in dual mode)
This applies to the entire system not just your card.
It looks as though the calculator was fairly accurate. As I mentioned you would probably be around the limit of your PSU but you should be ok. Coolermaster don't have the reputations of, say Corsair, for consistently high quality PSUs but your model appears to have favourable verdicts from several technical reviews. You should be ok, but keep an eye on things
Good luck!