Haven’t locked in to processor yet, but I assume it will be an AMD or Intel. So looking at mini-ITX and micro-ATX form factors.
Optical Drive? Haven’t committed yet, but I think at least a DVD is needed for the occasional install of a video game. I don’t anticipate any playback of Bluray disks directly, as they will be stored on the NAS.
ATX Form Factor
Micro-ATX Form Factor
Mini-ITX Form Factor
It doesn’t provide a bay for an optical drive, so that may be a deciding factor.