Two of the groups that got me started paying attention to acoustic music were the KT3 and the Clancy Brothers with Tommy Makem. Both groups shared two characteristics that, I believe, "opened the door" to all kinds of music for me - they had incredible energy when they performed and they sang great, both as soloists and in harmony. They made the music accessible to people who didn't know about that kind of music and could care less about "authenticity". I still use the same yardstick that I learned listening to them, when I hear something (or someone)new: Does the music sound good and does is move me?

They were and are great.
Bart