Babylon Sisters - Steely Dan
Fire and Rain - James Taylor
And a Female Singer, Amber Rubarth, Aimee Mann, Lindi Ortega, Brandi Carlile
I use the first two when I want to impress someone (older) who doesn't understand what really good audio sounds like. I have yet to find a song that impresses someone under the age of 25 (unless they play or sing themselves), all they ever say is, "Well, it's louder...."