Plus this is a deal of the moment a $20 off promo offer from Newegg good for today and tomorrow so that brings the final cost down to $389.99. Plus you get Evga'a "lifetime Limited Warranty". I can't believe we're seeing GTX 580's below $400 , so if your looking to buy right now this is one of the better card makers and a really good deal.
The stepup program and the lifetime warranty are two pretty good perks for a video card maker and I'm not sure but I don't think any other card maker has those options. They are valid and not just some gimick , I have taken advantage of both and as far as the warranty goes I have not run into a company that makes it so easy to do a RMA.
You can never have too much power but you can have too little. A 750w would be sufficient to run a GTX 580 and the minimum requirements for a 580 is a 600w psu. I would choose the Corsair over the OCZ and a better brand would be Seasonic or Antec.