I don't agree that the Red Sox need several bullpen arms. The only current RP free agent is Uehara, and I seriously doubt they'll let him go unless he retires. Taz, Miller, Breslow are under contract. They'd probably want to add one more guy for the bullpen, but they have a lot of depth beyond that.
The Sox's farm system and depth has been overflowing. For SP/RP options they have Morales, Wilson, Britton, RDLR, Wright, Workman, Ranaudo, Webster all for low salaries. If Buchholz is healthy, they have another arm available as well.
Assuming they don't trade a pitcher, they're probably around 130 million. That's 50 million under the cap. Unless they make a serious run at one of the high-cost players, they have plenty of room.