Not directly relating to your questions, but a couple of observations:
My main desktop PC gets the most use, and that's still running Windows 7, but that may get replaced by an iMac
If, as you say, you are already running Linux Mint, why not install that on your desktop instead of replacing it with an iMac? Also, a Thunderbolt docking station for a Macbook would kill 2 birds with one stone, so you would replace your Zenbook and your desktop with the Macbook, together with a docking station and screen of your choosing (doesn't have to be Apple). We use a few Macbook Pros at work (6 of those, 950 Windows laptops) connected to Benq monitors, and the combination is better than the iMacs they replaced (I'm told).
SD