knotknut :
From the Antec web-site;
Electrolytic capacitor aging. When used heavily or over an extended period of time (1+ years) a PSU will slowly lose some of its initial wattage capacity. We recommend you add 20% if you plan to keep your PSU for more than 1 year, or 25-30% for 24/7 usage and 1+ years.
http://www.antec.outervision.com/
Are they saying 25-30% for 24/7 usage and 1+ years?
Yes, but again it depends also on the amount of load that you put on the unit.
Most people have systems that will run thier psu between 40-60 percent of it's capacity when stressed and aren't running it like that 24/7.
If you're Folding you might need to worry about cap aging, otherwise a properly sized psu will give you many years of service.
Try running the OP's specs thru the calculator, add the basics ; 1 HD 1 OD a few fans and 25% cap aging.
PS; remember the number that it give's is a psu wattage reccomendation not actual consumption.