It's not that feasible. At that point, I'd almost recommend looking at some prebuilts. The OS will cost $100 (or $65 if you're a student). A $400-$435 build would be cutting a lot of corners.
I'm not saying it isn't possible, but give me a few minutes to look around...
The first thing I can think of is switching the case/PSU to this combo: Coolermaster Centurion 5 and OCZ ModXStream 500W
$60 after rebates.
EDIT: Here's another cost saver: X3 435 and Gigabyte GA-785GMT-USB3
$140. After that, you'd need to decrease the RAM to a 2x1 GB kit.