A friend of mine is shopping for a stereo system - she was at my place last week and wanted to listen to my stereo to hear what a half-decent rig sounds like. She thought my bookshelf speakers sounded good, but given her budget I advised her to get floorsanders to get better bass. We were listening to the opening of Bach's St. John's Passion, full of yummy contrabassoon in Harnoncourt's rendering.
"But these sound good enough."
"Try this and hear what you're missing," as I put my HD-600s on her head.
"... Oh. I want these."