Highly recommend silk liner socks underneath a thick pair of wool socks. A lot of synthetic liner socks irritate my feet (probably the antimicrobial treatments some companies use to make them stink less), but silk is great, and they are smooth, so easy to pull another pair of socks over them.
For merino socks, my favourite brands are Darn Tough, Bridgedale, and Fox River. The ones designed for running, cycling, etc are not nearly as itchy as old fashioned "ragg wool" socks. (the oatmeal coloured ones). Smartwool socks are cute, but I find they don't last as long as other comparable brands.
I'm surprised no one has mentioned like neoprene boots Muck Boots or Bogs. Both offer a winter version that's rated to -40 F. They are my most comfortable warm boots, though not as fashionable as a Sorel or similar. Lighter weight and more flexible, I find for walking long distances or driving, they're much more comfortable than a classic pac boot. Also, if you're in a climate where the snow is often wet/melting/slushy, they are fully waterproof, which I find invaluable. Oh, and mud hoses right off.