You already know my stance on this, but I'll state it here so others know why I'm on the "stand alone" side.
One of the main things we try to do when designing a system is timbre/tonal matching between drivers. There will be several different types of midranges that will be tested. Some will mate tonally well with the Dyn woofers and tweeters, and some others won't. My concern is that the test would naturally become a test on how well the particular midrange sounds with the Dyn speakers.
It would be EXTREMELY hard to not let that affect your judgment.
So, I say test them stand alone and let them be listened to on their own merits.