The Steelers should trade Sanders for a better 3rd round pick in 2013 plus a 5th rounder in 2013 or 4th rounder in 2014. The Vikings are the natural partner, as they coveted Wallace and now can have someone who is a more complete player for only 2.5 million.
This way Sanders cannot haunt us from New England, while the Vikings have someone somewhat comparable to Wallace for a fraction of the cost. (Remember the the Vikes were willing to get Wallace, if the stories are correct.)
The selling point is also embedded in the trade. Just considering the Vikes tells them that Sander is valuable. Then, both have similar interests: both the Vikes and the Steelers are not favorites to enter the Superbowl, however, both would prefer to meet each other in the Superbowl, so strengthening each other is not a negative for either side.
Another selling point: did Beliache not want Sanders? (And, despite disliking Beliache, everyone seems to think he is the genius in the Pots organization.)
So, trade Sanders to the Vikings for pick # 83 (2013) and pick # 155 (2013) or pick # 83 (2013) and a 4th round (2014).