I have a SG1, but IMO it is not SFF, a SG5 that takes a ATX would be nice... I do not agree with most of what qualifies for SFF...
You have just described the Silverstone Sugo SG13.
Built this to potentially replace my Asustor NAS:
Antec ISK-110 case
Asrock z77e-itx
4GB DDR3
i5 2500k
1x2TB 2.5" hard drive
1x64GB Crucial M4 SSD
Replacing the 2500k with an i3 3220 as its too powerful for this case. May end up getting another 2TB drive and replace the M4 with an MSATA SSD.
Pretty darn small and well specced for the size.
My Daughter's ST05 Lite
A case for PC the same dems. (maybe a bit deeper for GPUs) as the NES system might be cool.