Unless the 2nd hand part trade is alot better in the US than here in the UK I think O1die may be a bit generous there.
Agree with him totally though that staying AMD CPU would make sense if you want a better GPU. A phenom II quad (965BE) and a good cooler to OC it would weigh in around $150 and would work on that mobo then would leave you around around $200 or more for a better Graphics card.
I personally would overclock the athlon as high as you can and use that extra $250 for a modern gpu like a 7850. Then save up cash for a new build all together. That way you will still have a strong gpu to transfer when you are ready.