A couple of questions:
I thought the BXTs were the same height as the Kii stands so that the total height remained unchanged. In your top photo the Kiis + BXTs look taller than the Kiis on stands.
And, is the BXT on vs off comparison completely valid. With BXT off you effectively have the Kiis sitting on another speaker. Surely this would sound different to the Kiis sitting on their stands ?