Not sure yet on the GPU. Maybe NVidia GTX 275. Still gotta research for that yet, and ask here for any advice as well.
If your upgrading your GPU go with an ATI 5870 roughly the same price as yours but it wipes the floor with it trust me.
How much does a HD 5850 cost there?
The Corsair PSUs are the best on the market at the moment. 50+ amps on the cables and plenty of PCI E cables.