I don't know how to deal with 2x AGP slots. I assume they use 3.3 volts as opposed to the 1.5 volts used in most AGP 4x and 8x cards. With 4x AGP, using an 8x AGP card is simply a matter of taping over a few card edge connections. Obviously, computers using the older 2X standard and higher voltage levels could not be made to work with newer video cards.
This leaves me confused. If I'm not mistaken the old Matrox G450 and G550 cards are some of the few cards designed to work in any AGP slot (regardless of voltage).

Does anyone have an idea what the voltage requirements of currently supported cards are?
And what does the Pegasos supply to its AGP slot?
I'm not worried about later Powermacs as all that support 4X AGP should be able to use most recent video cards (with 8X cards requiring some minor modifications).
And, if the older Powermacs only support 2x AGP, is that so bad? I'm still very impressed with the Radeon 7500 and the Voodoo3 2000. 2d on the Voodoo3 is still competitive with many newer cards.