OK Apple fanboys, get ready to laugh at me. If you want a mini-priced Windows 8 machine that is not too stupidly huge and will work for a long while try the top Acer Veriton 4. It's in their "Professional" section.
Here's the deal. The 3.4GHz quad i7 is a real desktop CPU so it will run circles around a mini 2.6. I comes with a 1TB real 7200RPM desktop drive, has four USB2 and 4USB3 ports, has limited PCI slots, Intel HD 4000 graphics, a three-year warranty and Windows 8 Pro 64-bit.
We use W7 32-bit ones at work, they just keep cranking all day long, many of them 24-7. No medial slots, no awesome gamerboy lighting, no shiny plastic. Veritons are reliable, business machines for grownups.
Sure minis are great. I've got one myself. For a real, no compromised Windows 8 machine at a reasonable price I would take a Veriton over a mini any day.
PS. Next choice, without personal experience, is the newly released HP ProDesk 600 or EliteDesk 800. They've got 4th gen i7s and HD 4600 graphics.