To throw a new name out there, I will go with Zaza Pachulia.
Now, he is not someone I think is being actively shopped, but he could be a potential target, particularly if Atlanta makes some moves to get a new Center.
Pachulia is affordable, is a nice all around player, and brings some of the toughness and the enforcer mentality that we lost with Perk. He is not the defender that Perk is, but he is at least solid on that side of the ball, and I think he would be a very good player to put next to KG.