What good is that if you've got no real base of reference? It's great to be familiar with a given song as it sounds on your own speakers, but if you've got serious room problems, horrible speakers, etc and you've grown accustomed to the sound, what good is that really? It seems rather like trying to measure one line in the sand with another in meters, without having any idea how big a meter is... Granted, a concert isn't an ideal situation to get a reference for how a performer sounds, but it's certainly better than no reference at all. In the former example, maybe you've seen a meter stick in school once or twice...
Ultimately, I think this is probably the more effective way to evaluate a loudspeaker than the former, but obviously not everyone is terribly familiar with the sound of live instruments. The best thing I've got is a recording from the church in my wife's home town. I've been there and heard the organist and pianist play at least a dozen times over the last few years, so I know not only the instruments involved but the acoustics as well, and the quality of the recording isn't bad. Still, I'd hesitate to say my audio memory or my ears are that pristine...