I actually am running the Asus z170 now... but I updated BIOS and got this... Its not the greatest image, but my phone was having trouble focusing and the screen only stays like that for a moment...
It looks like it's crashing out at the SKL graphics driver (the Intel 530 driver) and you're using the iMac 17,1 SMBIOS.
If you had a fully working el cap system, did you have graphics patches in your clover config? If so, those patches were probably only valid for el cap; they probably won't work with sierra (the patches do a find and replace for specific binary sequences in the compiled kexts as I understand it, and that stuff can change between minor releases and typically changes for sure during major releases). I would look at the patches you have configured and try to remove most of them, while also simplifying your setup by using one monitor connected to the DVI out of your internal GPU.
FWIW this is why I always have two bootable disks, one to mess around with, and one known good one to fall back to if something goes wrong. You can also use the bootable USB stick for this purpose, but of course that brings you to the installer GUI, and I like to go to the desktop.
I'm still on el cap. My understanding is that for my board, I can do an update to sierra in place, but should anything go wrong I'll be ready to do a clean install.