I must say the Prometheus is the first pci board I bought and believe it or not, it does work better than the mediator on my A1200. I used red's pci cable adapters to add a voodoo3 and realtek nic card in my A4000 desktop without having to discard the PicassoIV in the lowermost/video slot and I still have access to two additional Zorro3 slots (I think there's a serial card and a sound card in them....it's currently in the closet atm). I did install one of those slot fans to help with heat but I ran it for a long while with the case closed and I still had flickerfixed AGA screens available (via the PIV).
If Jens ever releases the A4000 desktop version of his new FF, that would sort of replace the video slot lacking in the Mediator 4000Di design.