KG is really out of the question. Minnesota wouldn't trade him and they have no desire to. Nor is KG a free agent. Players like Maggette, Hughes, Artest, Donyell Marshall, and Tyson Chandler, would be easier to get. Hughes is playing great, but he may ask for a max contract that's out of reach for the Kings. In that sense, I think Maggette would be better choice, since he's a consistent player and he has an existing contract that isn't too bad.
With Mobley opting out and Bibby being unable to guard other PGs, a SG who can defend and score is a must for the Kings to acquire in the offseason.