I'm no expert, especially with your type of card, but here are some general suggestions.
Check your CMOS settings, to ensure that AGP is selected and optimized as your graphics slot. I am assuming the Rage Fury is AGP, and your 4Mb card probably was not.
Try re-installing your drivers, or checking ATI's website for any updated drivers. There were some new beta drivers for all their cards, posted early last week, I believe.
You didn't mention anything about your system's specs. Usually, when people see no difference in the performance of a new card, they're right! The problem is their existing rig isn't able to handle a faster, more detailed graphics flow. Having lots of RAM never hurts.