No. Online power calculators err on the side of caution because they assume you are buying a cheap power supply that can not put out it's rated voltage or can only do so at peak.. All the brands I listed are quality models that can put out their rated voltage continuously. All power supplies are not created equal.
That being said the Realhardtechx site also assumes you are getting a lower end power supply. Those numbers are conservitive as well. Most people really have no clue how little power a modern compter consumes. You have a 77w i5 3750K selected. So it uses 77 watts. Overclock it let's say by about 1/3 ( actually a little less ) to 4.4Gz and you increase power by a third as well. So now you have a ~100w CPU. It's not that linear but you get the idea, no need for an extra 200w power supply.
Some of the AMD FX chips need over 200 watts overclocked but that's one of the reasons they are such failures.
Here you go. One of the best units on the market for an amazing price. Fully modular and 80 Plus Gold certified. All you need for any single graphics card including the GTX 680 or HD 7970 and overclocking as high as you want.