What should I do?

[Nimrod]

I been thinking about upgrading my system I have

2.4c
P4p800
Geil 512mb memory (Other stick just died)
Fx5200
Fortron Blue Storm 400 watt psu

I have $500 to spend so I been thinking about getting

Amd 64 3200 or a 144 or 146 Opteron (around $150-$200)
Dfi lanparty Ultra D ($130)
Crucial Ballistix 1GB (2 x 512MB) ($110)

Then sell my motherboard, cpu, memory and use that money and the rest that I have to buy a 6800gs would this be a good upgrade or not?