The one thing that gives Salty and Lavarnway trade value is their position. There's just not that many good catchers out there. And while they both have holes in their games (Salty's inconsistancy at the plate and Lavarnway still being a prospect with defensive question marks) they still are better than many other starting catchers in the leagues. Now are they ever going to bring you a top 2 starter all by their lonesome, of course not. But they could both be big additions to a package of players.
As for Morales, if this was a few years ago, I'm sold. But after the injury, I don't trust him. It also hurts him in the field, turing him into primarily a DH. We already have Papi, and Napoli is your 1B now. I think the lineup is pretty much set at this point, with the only potential signings being a platoon mate for Gomes or maybe Drew. At this point they just need some pitching help. This lineup will score, we just have to hope the guys they pull in can help keep the other team from doing the same.