Need help for my Power Supply in my Computer Build

[esvada]

So here is my Computer Build:
http://pcpartpicker.com/p/CQjQBm
pcpartpicker says the estimated wattage is 328 watt is it true?
Do you guys think is should be using a 600 watt PSU instead of 500?
Someone says if you want to Overclock your Graphic Card you need a higher watt PSU is it true?

 

[popatim]

Since you cant over clock your processor, and only your gpu, 500w is enough.