To be honest I think both of those cards are going to perform about the same. The 210 should support some features that the 8500 won't.
Overclocking the cards will help a little but I think the main problem lies in the old Pentium 4 cpu. And you may encounter power issues. The 210's minimum recommended power supply is 300 watts and your PC has a 300 watt. So your at the minimum with an older power supply that probably isn't capable of generating as much power as it did when it was new. Will the card still operate with low power? Yes it will, but it won't perform as well as it should.
I use EVGA Precision
to overclock my cards.