Polypropylene works fucking wonder's in the snow & is AFFORDABLE. Had just one pair of it when I was using it & was nice and comfortable out in the snow. Only had the polypropylene & a thick cargo pant & fleece top on & boots/gloves/ect of course.
I hear Underarmour is good in the cold as well but have yet to test it. Can only speak from first hand experience.
Near the bottom of the page.
http://www.sealsactiongear.com/products_clothing.html