Your preformance will not be enhanced.
The stability does.
Please upgrade your PSU accordingly to the rated power of your Total Equipmant Manifest of your PC. (400 Watts to begin with?)
-- The next applies to AGP cards only! --
Is the AGP set to 2? (Or 4 if capable in your BIOS)
It should be set to the hughest level; for such card.
Is PCI #1 empty? (Should be, becouse of the IRQ bonding with the AGP bus)
Is memory write caching set to UC or USWC?
(Set to USWC, to be compatible with new cards)
If you have a Memory aprture size setting, set it to equal or double your Videocard's memory.
-- The next is common, and applies to Both PCI and AGP cards --
Have you setup a Swap-file that is double the size of your internal memory? (Could help a lot with overall preformance!)
Best to do it on a sepreate FAT 16 partition who has 125% capacety, so it will not get fragmented.
The +25% is to keep Windows from complaining about "Disk allmost Full".