My music prof doesn't care for the records by the Anonymous Four - he says their style is too clinical, not warm enough. But there are quite a number of good recordings out of Dufay's work - both secular and sacred. The Mass L'homme Armé (what they call a cantus firmus - all the parts based on a popular tune, in this case a song "The armed man") is probably his most famous work. I checked Amazon and they have a bunch of his stuff, by various performers.