While I think we all can agree that the quality of American voice actors can be better (especially when compared to the yesteryear of anime), the major problem is the fact that I'm a purist. You see, I don't understand how people can sit through an American version when their more or less just following an adaptation of the film...It can be quite rediculous to run the American dub and the Subtitles at the same time...Plus, the the Japanese voices normally more accurately fit the characters and their personalities.
But remember, as I said: I'm a purist and I understand that some people, however blinded I may think they are, don't believe the same way I do.
Basically, my answer to teh whole thread's question was: whoever they cast in the Japanese version will be fine, I'm sure...