I think the pronunciation largely depends on your own area and accent.
Trying to describe this in words is exceedingly difficult because when I write "Ah" someone else may say it differently.
I see people writing "Uh" but that sounds completely wrong to me, I suspect the pronunciation of "Uh" is different from mine.
I say:
Ahh - me - Gah
I suspect the only real way to find out how people say Amiga is to post audio samples.
