Hi Stacey,
Welcome to the discussions.
AGP slots do not have "power" supplied to them as such. I think what you might be referring to is an extra slot at one end of the AGP slot in later model G4's. This extra slot is neccesary to provide power and USB feed for video cards that have the ADC (Apple Display Connection) system.
ADC is a single plug to the monitor that supplies video feed, USB and power and was an Apple "innovation". The older Apple LCD monitors, with the clear surround, used this system as did the last CRT monitor that Apple built. Apple no longer make ADC monitors.
The ATI Radeon 8500 Mac Edition card does not have ADC. Therefore, it does not have an "extra leg" that needs to go into the extra slot at the end of the AGP slot. Therefore you can plug it straight into a (pre-ADC) Mac that doesn't have this extra slot.
Bottom line: you can plug this card straight into your G4 AGP Graphic Mac and run two monitors (one VGA and one DVI) straight off it. The monitors will get their power supply from an separate source.
As regards your original video card (ATY Rage 128), this was never intended to run more than one monitor. To run two monitors, you must replace this card with a more powerful one (such as the 8500).
Cheers!
Karl
