Funny Sony,
Most likely you have the EU/USA/Canada model, where the Japanese one is stating 2-16ohms. Both versions are the same, same mosfets, same transformer, same power supply, same rectifiers, minus a couple of electrolytic caps on main L&R boards (signal).
Please note that both versions drive easily SS-M9ED speakers, rated min 2ohms and 86db efficiency.
Late answer but i have seen it late.