The world of small form-factor PC hardware is divided between tiny kit solutions such as the Intel NUC (and the host of mini-PCs from various manufacturers), and the mini-ITX form-factor for system builders. The advantage of mini-ITX is its ability to host standard components, such as desktop-class processors and full-length graphics cards. However, mini-ITX requires a significantly larger enclosure than a mini-PC, and the "thin mini-ITX" standard has been something of a bridge between the two, essentially halving the height requirement of mini-ITX. Now, an even smaller standard has emerged, and it almost makes mini-ITX look big in comparison.
Any major computer upgrade generally requires a full software reinstall too. No so if you heed the advice in the guide to Upgrading a Motherboard without Reinstalling. PCSTATS Tips