Max Pachioretty + Mikhail Sergachev
For
Matt Duchene + Chris Bigras
Duchene > Max
Serga > Bigras
I should offer a little explanation for this.
For Montreal, they get Duchene to be their 1B center, playing a more valuable position than Max. Chris Bigras is easily NHL material now, but is not playing in the NHL now because of the amount of one way contracts that Avs defencemen have. Bigras is very intelligent, smooth skating defenseman with great passing ability and is clearly top 4 potential player. Both of these players would help you with Stanley Cup run.
For the Avs, they get a top 6 sniper who sounds like he needs a change of scenery and a market that does not follow his every move. Denver is great in this regard. Avs were very interested in Sergachev, and this would give them a legit prospect that could be a top pairing LHD.
Mtl fans always say that Serga is not tradeable because of Markov age, but Bigras is a good prospect himself. Its downgrading from tier 1 to tier 2 prospect, while bolstering your center depth and adding more defensive depth for this season by gaining an NHL ready prospect who wont look out of place. Bigras can play both left and right side.