600$ isn't that bad if you already have things like a monitor, mouse, keyboard, and even better if you can use an older DVD drive or HDD.
Here we go, budget build for you:
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.323863
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.328605
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.334441
http://www.newegg.com/Product/Product.aspx?Item=N82E16827136177
Plus one of
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102866
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102868
Cheaper video card makes 534.92+shipping after MIRs, more expensive one makes 569.92+shipping after MIRs.
This isn't from Amazon, but Newegg's better anyhow.