first mistake is $70 for a case that could go towards a GPU.
$500 is a sweet spot build actually:
Athlon II X3 450 $80
AS Rock 880: $60
WD 500GB: $40
4GB DDR3-1333: $42
cheap DVD burner: $18
Xigmatek 500W 80+ Bronze: $45
Rosewill Destroyer: $50
GTX 460: $160 (if gaming at 1680x1050 or less,get the 768 model, at 1920x1080, get the 1GB SE model)
I have a public wishlist on Newegg called "Tweaked SBM500" that is based on the last $500 SBM machine. It is very similar to the build ScrewySqrl posted. The ASRock 880G is currently Out of Stock, but should be back on 1/17. The GPU in it is a 768GB GTX460.