I second the notion about the <$525 thread, also about the 430W PSU. Thats plenty, you'd be able to get by with a 380W using a 6850.
As far as your OP system. You're on the right track there, it basically looks like the Econobox from TR's system guide. Your motherboard looks cheap for ASUS offerings. Maybe check out ASRock (ASUS' sister company) if you need that price but possibly more features.
Main: i5-3570K, ASRock Z77 Pro4-M, Asus GTX660 TOP, 120 GB Vertex 3 Max IOPS, 2 TB Samsung EcoGreen F4, 8GB 1600MHz G.Skill @1.25V, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Hand-Built Wood Case