pcDuino3 Nano.
A20 (1Ghz ARM CPU), 1GB RAM, 1Gb NIC, HDMI, MicroSD, SATA, USB,
5V 2A power, Arduino shield pinouts.
I don't recall this being mentioned in this group before, but it's supposed to have been available for a few months for $39. It doesn't seem to be widely available in the UK yet -- there's plenty of the earlier
So like the Banana Pi, it should make an acceptably good NAS, with its SATA port and 1Gb NIC. With limited support (in the English-speaking world, at least), there's again going to be a question about the stability of the distros (compared to the huge support for Raspbian).
That Arduino-shield compatibility is a definite plus. But as with other A20 boards, I expect that if it's going to be placed in a case, then a finned heatsink would be needed, and a large hole cut in the case for it.