bigtim,
My feet used to be the first thing that got cold.
I bought a pair of Rocky boots 1200g insulation a half size too big. I recommend a pair of polypropylene liners to assist in wicking moisture to the next layer which should be wool. Merino wool is my choice. The wool sock should have good bulk (hence the 1/2 size too big). Also, check the wool content of the sock. Some advertise merino wool but only have 20% wool. I look for 80% or more.
If the temps drop well below freezing you may be able to add another pair of wool socks or you might use a thin stick on, chemical foot warmer. I've donevery well down to 5-10 degrees with the polypro liner, 1 good pair of wool socks and a toasty toes foot warmer
FYI..Do not use cotton socks

FYI, Carhartt makes a very warm sock. The A111 arctic socks are 88% worsted wool and have decent bulk. They are $14 on the website. I actually found them at a Gabrielle Brothers last year for $3. I bought 6 pair. I would still buy them at $14 if i had too.