Here is a link to a power supply calculator: http://www.antec.outervision.com/
The result will be the total for the entire system and it will be overestimated because there are a lot of cheap, low quality psu's of questionable performance that people insist on buying.
Corsair is a high quality brand that consistently earns high marks in technical reviews and comparisons. The Corsair psu's are stable and very reliable. It's one of three brands most often recommended by veteran posters at this forum.