The big difference for me handling the cold, whether it is waterfowl hunting or deer hunting...has been my Sitka gear.
No matter where you go as soon as you mentioned Sitka, people comment awesome stuff but very pricey. Well a gallon of gas isn't worth 3 to 4 dollars a gallon either, and its the same gas we been using for over twenty years. With Sitka at least you are getting state of the art material with top research behind it.
That all being said, the layering system is the key with a good outer covering. To me the outer covering must have wind blocker, with a soft covering for noise. Nothing beats that than the fanatic system bar none...and if its severely cold the incinerator with a wool next to skin is all I wear with that system, almost too warm.
But the key I have learned is I never wear anything cotton next to my skin, no matter how hard I try not to sweat, it happens. The cotton traps all moisture and holds it next to the skin, and with no wind blocker the air seeps through the material leaving me chilled to the bone.
I know its a huge expense, but being able to handle colder weather longer and more comfortably without the bulk...that's invest I'm willing to make.