The power supply won't do anything for the performance. Going from gold to platinum would only give a marginal increase in power efficiency at high loads. At idle it will be essentially no difference.
People aren't saying it's a bad build because there are better parts. They're saying it's bad because in its price range there are ways to get way better performance, or get the same performance on a cheaper machine. He spent about $100 too much for the performance he would get out of the processor, and could have put that towards a $250 graphics card instead of the 750ti which would significantly boost his performance.