After searching for a month to get information on video cards for my PowerMac G5 dual 2 GHz (late 2004), I finally found a place with reviews on twenty-four AGP cards for this machine. His prices are great and I bought the top of the line card a *BFG* nVidia 7800 GS OC DVI/VGA for Apple Mac G5 8X AGP for $160.00. It is an altered PC card rather than a "Made for Mac" card, but this guy seems to know what he is talking about. I'll take out a SquareTrade warranty on it just in case.
http://old-macs.com