Something along the lines of
Intel Core 2 duo E6300 $187
Gigabyte ds3 motherboard $133
Evga 7950gt $200
CORSAIR XMS2 1GB (2 x 512MB) $111
NEC DVD-RW $29
$660 before psu, case, and hard drive. So you need a psu, Fortron and Hiper are suppose to be really good right now. Decide on a case and how much hard drive space you want. You should get near your budget but If you can fit it in your budget I would recommend 2gb of ram though. I'm assuming your budget was just for the tower and not the os and other stuff.
Also it seems like the 8600 ultra is suppose to come out at the beginning of March. IIRC the performance is suppose to be close to a 7950gt and has DX10 support if you were wanting that.