God... I wish I got a dollar everytime HPI magazine made these sweeping staements about Japan...
Take it from me, I've had more experience in Japan than the whole HPI staff put together:
It's Stay-gee-ah.
In Japanese, they write ステージア... now see that hyphen? It elongates the 'tay' sound in Stagea. Because it's elongated, it's possible that the 'gee-ah' part sounds like 'jah' if said really quickly, but that doesn't mean it's pronounced 'Stay-jah'... nor by a long shot.
And to those car import guys that go to Japan 3 - 4 times a year... I bet their Japanese lanuage ability ranks up there with their J-girl picking up skills