Further data, from my own 3dMark05 runs:
9800pro/P4@3.0:
3DMark Score2620.0 3DMarks
CPU Score3611.0
Return to Proxycon12.16 FPS
Firefly Forest7.45 FPS
Canyon Flight (SM 3.0)12.71 FPS
CPU Test 11.83 FPS
CPU Test 21.83 FPS
X800xt/P4@3.0:
3DMark Score5789.0 3DMarks
CPU Score3870.0
Return to Proxycon24.04 FPS
Firefly Forest16.92 FPS
Canyon Flight (SM 3.0)30.54 FPS
CPU Test 12.22 FPS
CPU Test 22.22 FPS
x1900xt/C2D e6600:
3DMark Score11995.0 3DMarks
CPU Score9081.0
Return to Proxycon52.17 FPS
Firefly Forest33.77 FPS
Canyon Flight (SM 3.0)62.7 FPS
CPU Test 14.89 FPS
CPU Test 24.89 FPS
A 9800 Pro is thus 1/4 the speed of an x1900xt, which itself is about 1/2 as fast as a 5670, which is 1/2 as fast as a GTX460-768, which is 1/2 as fast as a GTX580. Thus, your 9800pro is 3% as fast as a GTX580 (said another way, the GTX580 is 33x faster than your card).