Congratulations on your new speakers
400 watts is 400 watts, class A, class B, class of 42. A watt is a rate of doing work. 400 watts is roughly 1/2 horsepower. This rating is based on the woofers each being able to handle 200 watts and being perfectly matched. Exceeding 400 watts applied continuously DOES risk damage but 400 watts will produce an enormous amount of sound. As you will discover, the bass potential of these speakers when properly positioned and the music contains bass tones is awesome. However, the speaker cannot handle anything like 400 watts or 200 watts at higher frequencies. All of the other drivers can handle less. Still, in a home, these speakers can produce very loud undistorted sound levels. Either your Crown or Parasound amplifier should be able to do them justice.
I must admit that I didn't like mine all that much when I first got them. they were good but now they seem much better. Breaking in? Hardly. Adding additional tweeters, and properly equalizing them makes all the difference IMO. By the way, you might visit Classic Speaker pages at http://www.arsenal.net/speakers/ . You can get a lot of information about AR9 including the schematic of the crossover network and the discussion pages will put you in touch with among other people, the guys who designed them. BTW, you can also download the instruction manual there too.