I don't see why the Sox really NEED to re-sign any of those guys.
Jason Varitek: Good catcher, but last year was the first time in four years he put up quality numbers. Meanwhile, the Sox have a worthwhile catching prospect in Kelly Shoppach.
David Ortiz: Another good hitter, but he can not hit lefties, and he is best used as a DH. Why sign a guy long term to DH, especially when you need to platoon him?
Derek Lowe: Overrated. His K rate as a starter does not bode well as a top-flight pitcher. He put up a gaudy ERA and win total in 2002, but has regressed since. Are you willing to bet big money that he'll return to those numbers?
Meanwhile, a veritable shitload of free agents are available this offseason. Carlos Beltran, Magglio Ordonez, Jose Vidro, etc. These guys could help the Sox more than the aforementioned three.