If you have the normal amount of fans , hdd's , ram and if you have lights or any exrenal components that are drawing power from the psu through the motherboard. Why don't you list all the parts in you computer that use power. When a card manufacturer lists a minimumpsu requirement it's going with an average Pc build and then adding a few watts for cushion. Someone could add a water cooling system with a pump and additional fans for the radiator. If what you have is a normal build then the psu should be fine.
Will, I'm actually upgrading to a 620W SeaSonic Modular Power Supply, No worries anymore