Machka,
You really have to try the modified cheap snowboarding pants for -10 to -30 C conditions. They work very well. You have to find the ones that are lightly insulated with thinsulate or something similar. Then just sew the inside seams up a little at the bottom so they aren't so baggy in the lower leg.
You wouldn't think that they would work because they don't wick like tights next to your skin. This is true but I have found that by not wearing tights under them (just shorts) my legs don't sweat much but create this warm, acceptably humid environment for the legs. My legs don't get over heated or cold they feel just right.