Funny thing about the iMac I have, you can't turn off the embedded monitor and just run an external monitor. It seems the new multiple monitor situation doesn't

Funny thing about the iMac I have, you can't turn off the embedded monitor and just run an external monitor. It seems the new multiple monitor situation doesn't have any call outs for the iMac or anything sensible. I actually think they prevent this specifically in the sense that I should just want a Mac Mini or Apple TV and shouldn't doubt the ability to buy a way out of the problem.