I could never be a GM. Because I'd answer every proposal like this with Thornton retires a Bruin!!!!
After his handling of Rupp I think his stock as a fighter is currently higher than it has been (most boxers are in their prime at his age) if you feel he is one of the top 5 fighters in the NHL his current cap hit is justified and appropriate. Campbell is more likely to be bought out but he's played well so far.
That said in theory you could buy out both and replace them with guys who's cap hit will be the minimum and save almost 2 mil. I would be fine with letting Horton walk and buying out the 2 4th liners to get Perry in Black and Gold. Its probably what you need to do to fit them in without trading DK.
If you are having turnover in the lockerroom and losing key character guys (Horton leaving, maybe Ference/Boychuk moving on at some point) you probably want to do it all at once in the same offseason and not lose guys like those 3 + Thornton and Campbell 1 by 1 because then it will impact the morale and chemistry of team.
Adding a guy like Perry could speed up the breakout of Seguin to a dominant player if he isn't forced to be the biggest goal threat.
So next year's Bruins free agents are Horton, Rask and Ference (am I leaving anybody out?)
I am assuming that they will re-sign rask and he will get a raise if he keeps up his current pace, so let's say he goes from 3.5-5.0.
Ference is at 2.5, and I think you could re-sign him for about the same number
If you wanted Perry, you let Horton go, his cap hit is 4 mil.
Then you have Savard's 4 mil, and potentially Thomas' 5 mil cap hit (please correct me if these numbers are wrong)
So, assuming Rask re-signs for 1.5 mil annual raise, and Ference is re-signed for the same number he has now, then the Bruins would have shed 11.5 mil in cap space (one again, correct me if wrong, I am horrible at math).
So, is the issue that the cap is going down so much that they still wouldn't be able to add a pricey UFA like Perry, or are other guys on the Bs due for raises? or both?
If the Bs really wanted to sign Perry, I think they could find a way, especially if you opt for younger, cheaper players at some positions (such as Warsofsky or Bartkowski for Ference). That being said, I think they have shown a desire to build from within around the current core, so I don't think it would be something they actually look at, but there is always the possibility that they see a player like Perry as a great fit for their team.