no no i m upgrading my system currently i hve an intel dual core e2180 processor
I agree with willard, this new spec of yours is not really and upgrade. One may call it a downgrade, even. Your previous Athlon II X2 has slightly better performance.
But if you insist on your current 775 specs, going quad is the only way to improve significant performance. Even the cheapest C2Q lineup promises far better in term of raw power.
As for GPU part, if you concern for budget, I'd say no need to upgrade if you get that C2Q. Upgrades are usually justifiable if you go two or three ranks higher than your current hardware. As for that case, your $100-125 just won't cut it. You'll experienced a slightly better performance though, but just not worth the money. I say you should save them up some more and go for something like 5750 later on.
3GB DDR2? That's weird number, I must say. I suppose you're not really running on Dual Channel, as I imagined you use two differently capacity. Go for 2x2GB at exact same module-speed-brands, that should brings you some improvement as Dual Channel kicks in.