I think Siva will make a difference. Probably not enough of a difference to take them out of the basement, but the Hawks are absolutely woeful in the halfcourt, and Sivia at worst is a PG who should at least be able to get them into their sets, and gives them a guy who can make a play when the shotclock is ticking down too.
Harvey is a negative on the court at the moment, even having Coenraad sit outside the three point line with Siva/King would maybe be an improvement - hell, to be honest rolling with 4 shooters and a big playing 4-out simple pick and roll stuff with Froling or Mango would be better than what the Hawks have been doing to this point. It won't help on the other end, but the past two years the Hawks have been largely a one-way team, which is better than being a no-way team like they are right now.