CPU? SLI vs Crossfire? Ram? ATX? Post some more information.
Just built an AMD rig with: http://www.newegg.com/Product/Product.aspx?Item=N82E16813131013
Thats a pretty good bang for the buck.
Antec 900
Asus M2N SLI deluxe
AMD Athlon 6400+ 3.2ghz
4 gigs Mushkin DDR2 800
2 x BFG 8800gts 512mb @ 805/1024mhz
Creative X-fi sound
Corsair 750W PSU