How cold do you want to go? The best really cold weather gear I ever heard of was made by Northern Outfitters called the EXP system - a synthethic suitable for the high arctic, and also waterproof. They're defunct.
The next best thing is fur, but unless you're Inuit or an expert kabloona and know what you're doing, it isn't the best option. It is absolutely essential to layer to control how hot you get but mostly to control your sweat, because if you get wet in the remote cold you freeze. And probably die.
Base layer can be silk or some kind of polypro/fleece. I like Marmot, Patagonia or MEC, but the runners' stuff like Hind and New Balance is actually really good. Mid layer [if you wear 3]can be polypro/fleece or primaloft; and main layer for insulation - I think down is the best unless moisture is a real problem. If you are going near ice and snow, some protective shell is a good idea for the down. I like Dryloft rather than Goretex because it breathes better and if it's really cold you shouldn't need the extreme wetness protection of goretex. Pertex makes something similar called Pertex Endurance.
Who makes good gear? There are lots of makers. For Primaloft I love Integral Designs out of Calgary, and they do custom work, but MEC is pretty good for lighter pieces. For down, Feathered Friends out of Seattle, Marmot, Valandre and North Face all make good stuff. FF does custom work, though.
Wool vs fleece: there are arctic explorers who died because their wool clothing didn't cut it. I personally tripped in Northern Ontario for years in fall and my wool gear was brutal. I'm much happier in primaloft or fleece [but something has to be done to the fleece to cut wind like a nylon facing or, better yet, windstopper]. For pants, I prefer different material, either Spandura or a nylon/poly mix, of a goretex bib. Newer goretex xct, I think it's called, should be better because it's supposed to be 25% more breathable.
But for really cold conditions like high arctic or antarctic winter or on a mountain, thems that really know their stuff and whose lives depend on it, and that don't include me, use fur or down - and everyone layers, even the Inuit. That seems to be the key.
