If you can spend the money, nothing beats goose down for warmth. A matching goretex down parka pants set will keep you warm in extreme weather. But they aren't cheap. Expect to pay$100-250 for each. And gore tex is not the quietest material. But the windproof and waterproof preperties of the material is great! Cabela's is always a good place to look.Check with north face and MarmotThere is also a set of down long johns outhere made by someone.
If I am stand hunting (and sittitng still is when I get the coldest) I start with polypropelene long johns, over which is an army suplus layer of wool long johns. Then wool army pants (Swiss, swedish, czech, ets), and a wool army sweater (wooly pully british or US jeep sweater, etc). Next comes a one size larger wool shirt.Then an insslated wool shirt. Over all is a layer of army suplus goretex cammo pants and parka shell. Layers can be removed before the hike to the stand or as the day warms up. IF it is really cold, and I have to sit still for a long time, I will throw a heavey wool army coat over all. I can't really move too well in all of this but for stand hunting that is no big deal. My recipee is wool and polypro. Old world fibers used with hi tech materials.
Next year I may go with the down formula if I rifle hunt and have alot of money next year
okcmco