The Zotac ZBOX line of mini-PCs predate the NUCs, and have been filling that niche for many years.

The CPU is not that important so long as the graphics chipset is capable. So a ZBOX with an Atom is fine so long as it is paired with a discrete NVIDIA GPU chip. In the case of the all-Intel NUC thingies, the CPU and graphics are the same chip, so it matters more there.

No direct experience with a NUC here, but I have set up many, many ZBOX machines as combined MythTV frontend/backend PVRs, and they have zero issues with playback of pretty much anything. A NUC running Windows will probably be just as capable if not more so.

Cheers