The Enermax NAXN 450W and Corsair CX500V2 are basically the exact same PSU, so just get whichever is cheaper for you. Chaud's AMD based Puppy spends too much on certain components, but skimps on the graphics... A $500-600 PC shouldn't have a $100 mobo or a $125 HDD. I'd also say that an aftermarket heatsink is unnecessary (albeit it's actually one of the first things I'd add back to the system.)
Marest's build is quite similar to a suggested build I maintain:
http://secure.newegg.com/WishList/Pu...umber=10023331
They both feature an i3-21xx, 4GB RAM, 500GB HDD, HD 6850 graphics, and a budget 400-500W PSU. The biggest difference is he elected to go with a slightly more expensive motherboard with just two memory slots, whereas I decided a cheaper H61 based board with four memory slots would make upgrading from 4GB easier (cheaper).