All posted firmwares are compatible with eachother, only differences maybe supported languages and different bootscreens.
Official Emtec firmware
Official Me1000s MM firmware
version 2.0.8up (only English and German)
version 2.0.9up (only English and German)
Official Chili-Green firmware
Official hBox HMC-39 firmware
Official Emprex ME-1 firmware
This link was sent to me, thank you John B. It seems the Emprex is using another firmware compared to all the above types. This firmware is only for Emprex ME1. The installation steps are the same as the installation using usb stick described in the FAQ.
Official Ellion HMR-700A firmware
Ellion seems to use another firmware compared to all the above types, because it doesn't start from hdd. This firmware is only for Ellion HMR-700A.