Was just looking at some new calipers and saw these:
(Reman) Red powder coated dual piston calipers.
They are $54.79 a piece on Rockuato.com right now.
Search under 2006-2013 Impala calipers. They use the same knuckle as some (if not all) W-body's, so they should bolt right up. The only difference is that you would obviously need new pads and rotors.
You can get the rears also:
Rear- $62.79 a piece.