I've tried all the shoe covers and socks and the rest, and in the end there is only one thing that works: properly designed gore-tex winter cycling shoes.
OK, I think you may be right. I've tried all the other options, and thought I had it figured out with the chemical warmers. However, on a ride over about an hour, they seem to stop working, probably due to lack of air getting in there. I noticed when I stopped for lunch and took them out, they were cold again, but then when exposed to the air, heated back up.
Now that it's almost spring, I'll just tough it out and put off buying the winter boots until next fall. But that's my plan for future winters.