I like the tandem of Sully and Amir. (Zeller give way too much ground, and doesn't rebound well enough)
At least with Amir, we have some rim protection, and a good defender, and a some scoring. (also I think right now Amir is playing with a turned ankle)
With Sully you get a good rebounder, he scores, he passes very well, and he knows how to use his bulk on the beefy taller centers and PF stopping them from gaining position right under the basket. (I know conditioning cuts down his minutes) IMO Kelly is the solution there.
That said, it's certainly not a great situation, but it's what we have until we get a long term center.