Good points about the Mediator/Prometheus route:
-Voodoo3 gives more picture quality
-Its blitter is much faster than Picasso4 one.
-It has more gfx memory so more screens fit in ram without noticeable slowdown.
-You can fit cheap PCI network cards
-It's supported natively by AmigaOS4.
bad points:
-no monitor switcher
-on 4000D you lose video slot
-no MorphOS compatibility
-CV64 (the older ZorroIII only model, not the cheap "3D" one) bus speed is slightly faster