@Lemmink:
As I understand your post - the Grex manual states that you should NOT connect power to the power-connectors on the Grex, is that correct and do they mention why?
If so, it wouldnt definately not be strange if the BlizzardPPC or the A1200 motherboard would be fried when attaching anything more current-demanding than a network card to the Grex. The BlizzardPPC isnt specified to be able to supply more current than the BlizzardVision draws and the A1200 motherboard is probably not even speced to handle the currents drawn by the BlizzardPPC alone in the first place even... it should for example be a pure wonder that an A1200 motherboard with BlizzardPPC and a BlizzardVision attached doesnt burn on the spot... it shouldt atleast not go hand in hand with the term longevity anyhow.
/Patrik