What I have:

AMD Athlon 64 X2 Dual core 3800+ 2.00 GHz
Some asus mobo
4 GB RAM DDR2

What I'm planning on getting:

4 GB DDR3 Ram
AMD Athlon II X4 quad core 3.1GHz
Another asus mobo (: (Fits the athlon 2 and has a pci express 2 for my vid card)

Will cost me 252$ Is it a worthwhile upgrade?

My video card is a 9800GTX+ so i'm not planning on upgrading that for a little bit since it handles RIFT (the only thing I'm planning on playing for a while)