I HAVE been to Alaska, the Yukon, the NWT and was born, raised and live in BC; I have done LOTS of cold weather camping and I strongly recommend the following, based on owning and using bags from these makers.

The Western Mountaineering Puma or Bison, preferably the former as a -40 bag is pretty specialized. I have camped, solo, in January at -40 and I don't recommend it.

The Integral Designs Himalayan-XPD-II, a superb cold weather bag and you CAN get optional 900Fill down as I would.

The Valandre Shocking Blue, the finest sleeping bag I have ever had, used, seen or expect to see, or the Valandre Freya, Odin or Thor, depending on your desires in respect of cold sleeping.

Possibly a Feathered Friends Snow Goose

Look at the PHD Xero and Diamere bags, I am very interested in these and nearly bought one last winter, but, am going on reputation only here.

Stove, I like my Optimus Nova and my elderly MSR GK and the MSR Dragonfly impresses me, too.

You NEED quality gear for remote wilderness cold camping and this costs a lot, but, a gear failure could cost your life.......