I would suggest looking at ITX-boards and housing, then you could have a usable computer and an NAS all-in-one
External PlugPSU (2x12V to pico-style PSU board)
- Chenbro ES34169 ITX
- 4x 3,5" HDD on hotplug slides
- 1x low profile DVD
- 1x 2,5" SSD internal
- no LP PCIe bracket!
- watch out...