New iMAC looking for source
iPhone 6s Plus, iOS 9.3.4
Okay, you are doing the migration incorrectly. The most reliable method is to connect your Time Machine backup from the OLD computer to the new machine via USB. If you have a bootable clone backup you can use that too.
Then startup the new computer, when it gets to the point where it asks if you are migrating from another computer select yes and follow the on-screen prompts.
NEVER do a migration wirelessly! Why you ask, simple answer is it won't work!
Do not use a Ethernet cable (not reliable)
Doing a migration is extremely simple and fast if you use the backup from your old computer.
Turn it off by holding the power button on the back for 5-6 seconds, then turn it on and try going through the setup again.
On the new iMAC?
Correct.
Ok, did that and it's still stuck in the same place.
New iMAC looking for source