9700 PRO will deliver 90 to 95% of the performance of a 9800 PRO.
They are both 8-pipeline, 256-bit memory cards, the ONLY difference is that the 9800 PRO is clocked faster.
For the money, the 9700 PRO is definitely the best pick in the list you have.
For pure performance, the order from best to worst:
Ati 9800pro ($140 AUS used)
Ati 9700pro (I can get one for about $90 Australian USED)
Ati 9600pro ($115 Aus NEW)
Nvidia 6600LE ($150 Aus new)
Nvidia 5700 ultra ($140 Aus used)