At the moment it seems that AvalonMiner 841 is actually the most power efficienct choice, when you look at actual power consumption numbers. Have thought of buying a A841 from Blokforge? It's really nice and robust piece of gear. Anyways, I hope that -ck and Halong team gets better firmware version released and that it would improve the power efficiency. Canaan and Halong really are the best bets against Bitmain monopoly position at the moment.