Thanks a lot Alan for your response. Some questions that arise for me are:

o are the dispersion characteristics of the Axiom woofer and tweeter "similar". I assume there are frequency dependencies, but is the pattern identical whether vertical or horizontal (my main speakers are electrostatic speakers with a well defined beam... it is clear how much better they sound on stands than the floor).
o regarding drivers and other surfaces "interfering" with each other. I was once given the analogy of throwing two stones in a pond for bass cancellation with subwoofers. Is this essentially the same thing that occurs at higher frequencies, or are there other factors involved?

I have very limited knowledge of this area.. thanks for helping (I will also do the tests you suggest...).