shuttle an35n ultra- $62
amd athlon 2400 Mobile- $77
1x512 pc 3200 buffalo tech or crucial- ~$88

that about $230 for a nice upgrade. You might be able to hold on to the graphics card. I would test it and see what results you get. If you need more, now or even in a month or two you should be able to find great deals on the 9800pro. If money is a limiting factor, the list above would be my priority. That would give you a cheap rig that could easily last a couple of years if not longer, especially if when you need more speed you o/c that cpu and get some nice cooling.

Good luck man