As far as I'm concerned, about the best cold-weather boots you can find are by
Sorel. In fact, they are "The boot of choice" for Antarctic Service, and they offer several nodels. I've never been to Antarctica, but I've spent lots of 30-below time out in the Northwoods in my Sorel Blizzards ... plenty warm, plenty sturdy, but sorta pricey. You do get what you pay for though.
If you go with Sorels, you'll wanna get a pair of uninsulated overboots, though ... I don't think there are any knee-highs in their line.