I'll second the recommendation: some of the music from the Ar Tonelico series is remarkably good stuff, and I listen to it regularly. Most of it could be used as sacred music, easily.

The one problem with the Ar Tonelico music is that it's hard to get a large group of people to sing it, because the harmony is too tricky for untrained singers. My favorite sacred music is the hardcore religious Christmas carols, when sung in a simple form by a group of ordinary people. It's a hell of a lot more fun than any professional rendition of those songs, with the exception of Sufjan Stevens, who really gets it.