Kicking back and listening to your favorite records is the best way to break in a new set of speakers! It takes more than 20 minutes, but give it a few days and your ears will eventually train themselves to "know" what a good recording is supposed to sound like on those speakers. Believe it or not, the kick-back-and-enjoy technique is actually based on real science and is more effective than all the scientific measurements you might undertake.
Just be sure to adjust the volume so you're listening at the same levels you normally mix at.
I think you'll enjoy those speakers, especially given the great deal you got. If nothing else, you now have those cool white cones like all the big boys.