Hi,
Just a quick note on the ATI Radeon series. The Radeon 9700/9800 series devices are PCI/AGP compatible, there are some mode select pins IIRC that are set by the manufacturer to force the card to operate in either AGP or PCI mode, providing the card is degined for the right slot!
In my testing, mentioned in the post, I have used an industrial PCI graphics card that supported the 66 MHz PCI interface.
Ian