I think there a lot of theories, just like in any field.
One theory is to match all the drivers on the speakers.
But in reality, as you and GlocksRock have stated, the driver-size matching is not critical at all.
The CLR3000 is certainly one of the best speakers period, as confirmed independantly by Tom Nousaine/Sound & Vision Magazine.
I bet if we matched the CLR3000 with any system out there, it would sound great.
They say the Center channel gets > 50% of all the movie soundtrack.