I built this system about a year and a half ago and just wondering what I would need to upgrade to get UT3 running at some good FPS

AMD Athlon 64 - 3000+ 2.5 GHz
GeForce 6800 GS - 256 MB

I probably need to upgrade my Motherboard so I can handle a dual core processor and definatly a new Graphics card...
Any suggestions? I really don't want to spend a lot of cash seeing as this game is the only reason for me to upgrade. The demo runs OK with 50 screen rendering or whatever its called. And runs horribly slow on 100%.