Mike Wallace would be a great add. It would help Rice and rest of the WR corps, not to mention Zach Miller. Look what he did for the Steelers - Brown, Sanders, and Heath Miller. He would be a boon for the passing game.
Wallace was never in the Superbowl when the Steelers played the Seahawks but he could be in one as a Seahawk soon (if they sign him). I heard from many sources radio, tv that the Steelers are not planning on putting the franchise tag on Wallace.