Best I can tell you is...
$150 on the CPU (Along the lines of a Athlon 64 3200+)
$150 on the video card (ie; a GEForce 6600 or around that)
$50 on the PSU (Antec SmartPower is a good choice)
$100 on the RAM (ValueRAM, Kingston or Crucial)
Cheapest case you can find (Around $20 bucks)
$50 on the Hard Drive (IDE, or SATA if you can find one cheap enough)
$30 on the CD/DVD Drive
And even that is 550. Just make sure you're getting the best possible deal on that item, and SHOP AROUND. Don't settle on the first thing you set your eyes on.