Ok, using a radio shack spl meter and white noise, I level matched the duet headphone jack to the m3 headphone jack. Realizing that the m3 is balanced, using cinemag transformers to balance the inputs. The m3 has better bass control, better details, and is more "full". But the duet headphone jack is no slouch. And it's a LOT smaller.
First few minutes of testing says duet is a nice portable solution (while nowhere near as portable as the pico ). Comparisons with the pico will begin when the package from california gets here. And of course, extended listening will happen with both, I just figured I'd post initial duet impressions.