There is still NOS (New Old Stock) of both ATI and nVidia AGP cards in the 4x/8x version that have up to 128 Mb of their own memory. Checking various stores such as NewEgg
or Ebay may yield results. A 5200 series may not be suitable, but may also be your easy ticket to joy with updated drivers. Going with an older PCI card would not provide desired results, as the bus speed is limited to 33 Mhz. The AGP bus speed is double that. The differences in the 2x/4x/8x ratings is due to how many data ticks are in each clock cycle. While the AGP slot may accept the card, the mobo chipset features would not properly accomodate it.
While that "Tiger" is a great board, you are limited by its 1 Ghz speed maximum. If your case is a standard ATX, consider one of the Socket 478 mobos from NewEgg
or other sources. You could achieve up to 3 Ghz speed, and true 8x AGP use. A recertified mobo is usually just as good as a "new" one. But you would have to include memory in your upgrade. You may come out under 200 bucks for a more modern system.
F@H.. to solve mankind's maladies.. in our lifetimes!