I was looking at this week. I have a i5 3750k and a full size atx motherboard in a define R5 case. The thing is huge, and seeing as I dont game on the PC anymore was looking at downgrading.
Tried a new Skylake Brix and it was slow at certain tasks compared to my current setup. It also had strange artifacting at 1440p. So I sent it back
I then started looking at getting a micro atx motherboard and smaller case. As you say they are thin on the ground but they are around if you look. Best I could find was a Asus P8H77-M PRO H77 Socket 1155 for around £78.
Think I will just stick with what I have for now. I would end up costing me nearly £200 and for what, the exact same performance in a slightly smaller footprint. ill give the Skull Canyon Nuc a go when it comes out