For your video card, use this article to find the best card in your price range.http://www.tomshardware.com/reviews/gaming-graphics-card-radeon-hd-6870-geforce-gtx-570,2834.html
For PSU, buy at least a 600W name-brand power supply. (Thermaltake, Seasonic, OCZ, Corsair, FSB, ect.)
For the case, it doesn't make as much as much of a difference. Just get one in your budget with the features and looks you want.