As far as PSU calculators go, you'd probably be better off setting everything to a maximum setting. That is, 100% CPU Utilisation and 100% system load. Although you're not likely to hit this, it gives you the maximum possible value that you could need. And when it comes to PSUs, too much is better than not enough. Whenever a PSU Calculator is used I always tend to increase the given result by 30-40% since different calculators give different results and this gives you some headroom.
Without using a PSU calculator, the official recommended power requirements for your graphics card are:
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 whole system.
If you're doing heavy overclocking etc or just want the extra headroom then you may want to go with something around the 700W mark. Corsair, Seasonic and the newer Antec models are known for delivering consistently solid and reliable PSUs so these brands are recommended.