For a quick update - I could no longer stare at the EP-800 sitting idle. It was fired up Friday night, and over the weekend, several movies were watched with both the Legacy's and the M100's, along with some additional listening to music.
The addition of the sub was quite helpful in music - and was so on both speakers.
And the EP-800 is quite the sub. Not enough time has been spent with it for a real review - but it had no trouble shaking our basement theater on Lord of the Rings, Two Towers.
And on music, it never "got in the way". It just extended bass, and by taking the signal below 60 Hz from the speakers, both experienced a deeper soundstage and improved vocals.
There will be more on all of this as time permits.