If you have a tuner, you use that for extended break-in sessions.
My theory is this: If a speaker sounds good right out of the box, it should only get better with break in. IME with the Ohm Walsh 2000s, there were odd sonic characteristics that came and went during break in, but they never really sounded bad, especially once a friend helped me reposition them.
I would suggest you play the Mirages as much as possible in the two week period, and when you're listening, try out all kinds of familiar recordings. If you're still grinning like an idiot after two weeks of that, the Mirages are probably keepers. If you keep them, and then lose your enthusiasm later on, I think you got them cheaply enough that you could sell them without taking a big hit.
Speaker selection should come before amp selection, so if you keep the Mirages because you like the sound, you can upgrade to more powerful amps in the future. That will probably expose another week link in your system. Welcome aboard the upgrade merry-go-round!