The Darvish trade shows me two routes of opportunity. One is taking on some payroll from the Cubs for MLB talent. The other is selling off to the Padres who are absolutely loading up. One will get you prospects, the other might cost you some.
With the Rays moving Snell, I'm all in on the former. There are a lot of Cubs players who would make the Sox better. I don't see them bringing back Rizzo with Dalbec and Casas, but Bryant, Baez and Hendricks would all be big additions, and might be had fairly cheap as far as prospects go, especially if Boston is willing to take back Heyward, Kimbrel or both. Think the Nick Punto trade, but in reverse, and with the "good" player in the Adrian Gonzalez role only having one year of contract left.
I would also consider trading with the Padres as well. They are going all in to be in the conversation with the Dodgers, but LA is still really good. Could a couple of pieces from Boston help? I'd think about moving some of the guys on the roster while bringing in others from the Cubs. First up would be Benintendi, Chavis, some of the other 2B types or even Martinez. They won't bring back Gore by any stretch of the imagination, but the Padres haven't been shy about moving their tier two talent, and a couple of pitching prospects would likely make that worthwhile.
Mostly, I want something to be excited about with the Sox. The NFL season has been a downer, and while I will watch all the games, I can't get too excited about the Celtics until playoff time given their runs the last couple of years.