I had not heard Franz Biebl's Ave Maria before, but now I'm in love with it. Here it is performed by Chanticleer:

If you prefer the sound of female voices, may I offer this performance by the Pro Musica Girl's Choir. I don't know who they are, but I like the sound, and the setting is beautiful, too.

I haven't heard a male-female choir that I thought sounded as good as a single-sex group, but this one is still good (De la Salle University Chorale in Manila).