Not signing Turris and use him as trade asset to upgrade the Center position was the correct decision.
So basically, we "only" used a "supposedly" late first, an average prospect (late 1st from a draft that wasn't deep at all) and a 3rd to acquire Matt Duchene. The plan was obviously to fill the void at #1 C for many years to come by signing Duchene long-term.
The problem wasn't the move in itself when it happened because if it worked it would have been well worth it (late 1st + meh prospect + 3rd to upgrade Turris to Duchene). The problem is the team didn't work out as a whole (so the first became a really good piece). Sens had very good players (Stone, Karlsson, Duchene, Chabot, Hoffman, Pageau, etc) but there was also major holes in the line-up (no replacement for Methot and MacArthur, shaky goaltending and cheap/wrong coaching staff) so in hindsight it's not super surprising that it didn't work out. It could have worked but it was a big gamble because it's very hard to compete year after year in this league when most of your opposition do as much as possible financially to be competitive.
However after a successful stay with the Sens (107 pts in 118 games), Duchene got traded and returned the 19th OA pick (Thomson), Vitali Abramov (good prospect) and Jonathan Davidsson (we'll see after his injury but could still be a good support player)
Abramov is a better prospect than Shane Bowers and Davidsson was also better to have than a 3rd (could change because of injury issues), so basically the end result of this is the downgrade of the 1st round pick (4th OA to 19th OA) and NOT have been stuck with Turris new contract.
4th OA >>> 19th OA
Bowers < Abramov
3rd < Davidsson
Having Turris < Not having Turris
It's really not as dramatic as some are saying but obviously the pick downgrade is a major loss considering the rebuild. I wonder who we would have taken 4th OA