I consider Ladysmith marvelous. But the last time I heard a completely a capella group live, I was a little disappointed. It was a younger male group who are regulars on Martha's Vineyard. They could definitely harmonize, but their doo-wop arrangments were such a complex jumble that you were lucky to decipher a word that they said.
Just had to enjoy it some as pleasant sounding instrumentals, I guess. : )
                        Dean