BLACKHAWK! Warrior Wear Black Ops Boots - BLACKHAWK!
I don't think these are insulated, and I'm not sure what you're going to use them for, but when I worked for a private ambulance company I wore these year round and they were the most comfortable boots I've ever worn. Plenty warm regardless of the weather. Just get several pairs of those Nike moisture wicking socks to go with the boots and you're set. My feet get cold easily due to sweating, but with those socks and this pair of boots, they rarely do. If they get cold, it's usually because I haven't been moving for more than 30 minutes... so I get up, walk around for about a minute, and they are plenty warm again for a long time.
Expensive but worth it, especially if you spend 12 hour shifts in them. I got mine for $95 instead of $180, so that was even better.