I also prefer at least two thinner layers to one thicker one so I can fine-tune my body temperature better. My insulation layers are a wicking base layer, a 100-weight fleece Montbell Chameece vest and a Montbell UL Thermawrap jacket. Important accessories are my polypro fleece balaclava, thin polypro gloves (that I don't have to take off for camp chores, the problem with thick gloves) and rain mitt shells. Using these in various combinations with a lightweight windshirt and/or my rain gear keeps me warm and dry (from inside as well as out). It's really important not to sweat while actively hiking in cold weather--the moisture inside can degrade your insulation just as badly as water from the outside. I can put the whole schmear on at once and be comfy in a 10* F blizzard. I also prefer synthetic insulation layers because my sleeping bag is down and I am unwilling to put all my insulation eggs, as it were, in one basket. I have thought about switching to a down parka, but I'd still want the vest for active hiking in cold weather and I'm warm enough with what I have--why spend the $$$ to save maybe an ounce?

Your mileage, of course, may vary!