If you have a good CPU you will get a big boost in performance! If you're CPU is not fast, you will not use the full potential of the Radeon 9800 PRO.
Check the benchmarks in this article :
<A HREF="http://www.tomshardware.com/graphic/20031229/index.html" target="_new">http://www.tomshardware.com/graphic/20031229/index.html</A>
You will notice that the FX5600 and Radeon 9800 PRO are not on the same league, Radeon 9800 PRO will kick the butt of your FX5600.
Lookin' to fill that <font color=blue>GOD</font color=blue> shape hole!