Mac – Is a 2014 Mac mini fully compatible with Sierra

1. Buy the "Basic" (as they call it in Apple Store) 2012 Mac mini and replace HD and RAM yourself is the most economical way. It's also the power user move.

a) While leaving the factory HD in place, you can put in a second drive such as a SSD at where the optical bay used to be. You can dual boot two OS X installations. One can be the daily OS, the other 1) as extra storage for less frequented files, 2) as Time Machine backup location, and 3) as beefed-up Recovery Mode if the primary fails. I don't know if you can put a 2nd drive into the 2014 model.

b) Dual drive and merge them into your own fusion drive.

c) Upgrade to a 3rd-party 16 GB RAM. The price cannot be cheaper given the amount of time it has been out in the market.

2. Haswell's raison is saving energy. It makes a lot of sense on MBP and MBA. And 2014 Mac mini DOES use less power than the 2012 model, but that's a moot point.

Compatibility is less concerning if you consider performance. An iPhone 4 is compatible with iOS 7, but that's not preferable, and a 4S can technically run iOS 8 but only sluggishly and without many features. You COULD install Yosemite on 2009 Mac mini, but would you do it?

3. Great. I fixed/tweaked my MBP, Mac mini, and MBA for 4 years now without ever going to the genius bar, hat in hand. So apple's support did a great job of staying out of my way. I'm serious. When I had a Dell, I chose to add years to my warranty because the company is the the only place you can turn to. Because apple has sold so many and kept its lines simple, there ought to be somebody out there doing what you're doing.

I don't know if you agree that Apple has placed Mac mini into that peculiar spot in its line-up: iPod Touch is the thing that's not an iPhone; iPad mini (2014) is that thing that is not a iPhone 6 Plus. Mac Mini is the thing that is not a Mac Pro. Apple's not going to be pushing the boundaries with it. That's my guess.

As a test server with multiple VM running, definitely quad core is much better than dual-core. None of the new features introduced in late-2014 mac mini benefits you.