If we were to bring in Wilson, Abraham, and perhaps Freeney, not only would be adding talent, but we'd be bringing attitude and swagger.
Fact is, swagger breeds swagger. You'd then have Abraham and Wilson, two guys with an attitude. Combine that with Spikes and Talib if he returns, along with Wilfork and McCourty, both of whom carry themselves with a bit of pride, and this attitude would begin to seep into the entire defense.
They'd have a confidence to them, a fire, and would play with attitude. It'd finally be a defense that isn't mentally or physically soft, but a defense that offenses don't want to face... because of fear.