For OCing, go with the DFI Lanparty nForce 4 Ultra.
Nice video card.
For your CPU go with the Opteron 144. Doubled L2 cache and OCs at least twice as well as the Athlon 64 equivalent.
Solid memory, but if your OCing your going to need some more powerful Kingston or OCZ at a minimum.
For your HD, go with SATA 150 and a 120GB, unless you think you'll need that much space. I'm just trying to keep it in the same price range since Ultra ATA costs a little less since it's an older technology.
For your PSU, get the Antec Truepower 2 550watt.