thats a nice budget PC, but you really dont need more than 4GB ram, you should buy 4gb ram instead of 8gb and get a 890 chipset motherboard, also i reccommend a ati 5830, here in the UK, the 5830 outperforms the 450 by a long shot and is yet cheaper!
My another vote for a PSU change.. Also your hard drive.. I guess it is a 5400 RPM hard drive which itself is quite slower compared to a conventional 7200 RPM hard drive.. And the power savings are really not worth it.. So get something like a Samsung Spinpoint F3 1TB.. Rest of the build looks fine..
+1 Emperus. Also, you may want to fill out the build advice form - if this is for gaming, the Phenom may not be the best choice. The 450 also falls into that category. That case doesn't strike me as the highest quality. Lastly, IF you stick to AMD, maybe get a more modern chipset, 800 series.