Doesn't really matter - ATI are now in a state of playing leap-frog with Nvidia, so we'll see cards from ATI that do similar things soon. In any case, AGPx8 cards won't work at all on AGPx2 motherboards (different voltages), and Nvidia aren't developing Amiga drivers either (or letting anyone else).
Hmmm - here's a thought. There won't be any drivers for the Amiga, *but* there are drivers for the Mac. All we need is for some clever haX0r to write a compatibility layer and we can use Mac Nvidia drivers...