Hi Drew -- I just happened to stumble across your post after spending some time trying to get Pages to do this exact same thing. An important point here is that you are not merely using bullets for decoration; they are numbers serving a functional purpose. Namely, indicating to the reader what section number the centered title corresponds to. While bullets are nearly meaningless in a centered list, a number next to a centered chapter title can be both useful and attractive.
If you really want to take full control of your organization and structure, I recommend you take a look at MacTeX (
http://www.tug.org/mactex/). It's got a learning curve, but can pump out truly striking documents, without deciding for you how your chapter titles are supposed to look. I've been using it for a while to typeset mathematical equations for presentations, but lately I've discovered that it makes a pretty classy word processor as well.
Good luck!
Will