Indeed I am right about my recommendation. The specs rated on the power supply, and that calculator (which you would know had you took more than 30 seconds to spec a system out and use the tool) puts the system at 90% load with capacitor aging as well as heat and other stress.
No idea where you're getting 500 watts for the video card - manufacturers of video cards don't list the power supply requirement of the card based on how much wattage the card uses, but on what the TOTAL SYSTEM will use. As you can see, 500 watts minimum for this card is well within the 700 watt recommendation.
I also did take into account the fact that he'll update his video card, and if you look at the history graphs, you'll see that while video card power requirements are going up for multi videocard setups, single cards continue to use less and less power for the kind of work they do, which also thereby makes your point at "buying ahead" irrelevant.
I'm also a gamer. I build systems for people who are gamers. I never use more than 700-750 watts. Their systems are still functioning to this day, and several of them have upgraded to faster equipment with no dire consequences.
I also do this professionally, for a company that builds our own computers. While we don't build them to play games, we do build them to be long lasting and capable in 5 years. I also work with servers with significantly more hardware in them than your average desktop PC. One of our newest servers is a 24 threaded monster with 7 hard drives, 32GB of RAM (with room for more) and it uses a 540 watt power supply (redundant, natch) which is still further proof that people overbuy their consumer hardware.
I like Guru3D, but only someone grasping for data to make their point would rely on just one website. I don't know how many years experience you have in this and I don't care - but my experience has shown that the more someone runs to their defense and says "I know what I'm doing" has something to prove, and it's not someone else's interests.