I have the Crispi Hunter GTX. They have 200 g of insulation which isn't much. I wear a liner sock, and a heavy wool sock to keep my feet warm. I hunted in knee high snow two years ago, and my feet stayed warm. Last year it was 40 degrees in the morning (no snow) and warmed up to 70 in the afternoon, and my feet were comfortable.
Your sock system will make a lot of difference. If you have a lot of insulation, but wear cotton socks (that don't wick) when your feet get wet from perspiration, your feet will get cold. You need a sock system that will wick the perspiration from your feet. I found my liner sock (Kenetrek Ultimate liner), and my heavy outer sock (Kenetrek Alaska wool socks) work the best for me.