After 19 years of cycling in Alaska, I think I've tried just about everything. As other's have mentioned, wiggle room for your toes is paramount. Also, consider stepping off the bike when your feet begin to get cold and walk/jog for a bit. That'll increase the circulation quickly. Just don't wait until your toes are frozen. I've had good luck with heated insoles and, or heated socks with an insulated winter riding shoe or cold weather specific shoe cover. Enjoy.
c