Ken, I'll take a stab at some of this. First, you can't "tweak" the EQ results other than selecting "Music" for a flat treble response or "Movie" for the "Audyssey" treble curve which has about a 2dB/octave roll-off above 4KHz.The calibration results, particularly raising the crossover frequencies, can be changed.
Audyssey doesn't add any reverb. DPLII and similar processing extracts out-of-phase ambience from the front channels and sends it to the surrounds. When Dynamic EQ is on, the relative levels of the surrounds changes with overall volume levels so that the surround effect is more consistent.
I'd suggest the Music setting for most material, and trying Movie for something which seems to be too hot in the treble(not necessarily a movie).
