Another vote for 8600GT. 8500GT if money is tight.
Disks: Seagate 7200.10 500 GB or WD5000AAKS (Wester Digital Caviar 500 GB) have great performance and price/GB.
If you don't have any FireWire devices (camera, etc.) look at the GA-P35-DS3R too, it's cheaper and it has 3 PCI slots instead of 2.
(Or get a GA-P35-DS3R and a PCI card to provide FireWire, if you want).