There's a little dispute in our family about this. My SIL from Spain pronounces it Ah-MAH-dee-o, and DH's Italian uncle pronounces it Ah-mah-DAY-o. But neither is willing to speak about what the "official" pronunciation might be.
I know there may be more than one legitimate pronunciation, but it seems odd to me that the Spanish and Italian would differ (although I don't speak either, so maybe that's my mistake?). I also know, based on my internet research that Ah-mah-DAY-o is legitimate. Anyone know if Ah-MAH-dee-o is?