Why it works: It's hard to see how it does for the Flames other than to pad out their forwards with another bona fide scoring threat to push them over the top. Duchene could easily move onto the top line at RW (he is on record as preferring to play RW rather than LW even though he is a left hand shot), and still gives cover at centre. Andersson is a comparatively easy piece to part with as the Flames are pretty well set on the RHD.
Why it doesn't work: It's hard to see the need for Duchene in the Flames line up other than as stated above. The Flames are very light on LHD so Kylington may be tabbed for a spot there. Any trade they make for Duchene will require something sent back of value or salary retained by the Avs to keep any kind of cap space hence the addition of Bennett.

Why it works: Avs acquire a potential Top 4 LHD in Kylington that is reputedly a big part of the asking price. Is he ready yet? Probably not but the Avs have a few who can hold a place on the left for now until any question marks are resolved. Andersson slots in nicely on the 3rd pairing for the Avs on the right. Bennett gives the Avs a nice young roster piece.
Why it doesn't work: Sakic may want more whether you think that’s reasonable or not. I suspect he will. Kylington may still be too much of a gamble. Bennett adds yet another centre to the Colorado roster (making about ten I think if you include Toninato & Kerfoot as recent signings!)