I have a later Power Mac G4 MDD with its original 64MB ATi Radeon 9000 Pro. I want to upgrade the graphics card in it to something more powerful. What is the fastest video card with the most video memory I can install? I found from somewhere that this Mac is only capable of seeing and using 256MB of video memory, but I can't confirm it anymore. Does anyone have any tips as to what brands and models I should be looking for?