I think there should have been more choices. Personally, I notice when words are not spelled the way I'm used to, but it doesn't bother me that much. However, with respect to two of the words used in the OP, I have the following comment;
To me, center is the middle of something, so it is appropriate for a (loud)speaker. Centre is an auditorium-like place where one goes to see the arts, performing or otherwise. A theater is where one goes to watch a movie. And a theatre is where one goes to enjoy the symphony, or a play, or opera. So its really four words in my book.
