Earlier quoted context omitted.
these little boxes are perfect for my home My use case is a backup server for my macs and cold storage for movies. 6x2Tb drives will give me a 9Tb raid-5 for $809 ($100 each for the drives, $209 for the nas). Very quiet so I can have it in my living room plugged into my TV. I have no room for a big noisy server.
While I get your point about size, I'd not use RAID-5 for my personal homelab. I'd also say that 6x2TB drives are not the optimal solution for low power consumption. You're also missing out server quality BIOS, Design/Stability/x64 and remote management. However, not bad. While my Server is quite big compared to a "mini" device, it's silent. No CPU Fan only 120mm case fans spinning around 500rpm, maybe 900rpm on load…
What would you use instead?
ZFS is better than raw RAID, but 1 parity per 5 data disks is a pretty good match for the reliability you can expect out of any one machine.
Much more important than better parity is having backups. Maybe more important than having any parity, though if you have no parity please use JBOD and not RAID-0.