Im not sure what the "best" are. I have Lacrosse's and some wigwam wool socks and they have worked pretty good. However im in NC and the coldest its gotten to this year while Ive been hunting is low 30's. In the past ive put on layered two pair of wool socks and my feet started sweating while walking to the stand. While I was able to sit all day towards the wanning hours of daylight it began to get uncomfortable. Make sure you leave enuff room for your feet to circulate. Hope this helps. Best of luck on your purchase.
I have Danner Pronghorn's and I wear them with the Smartwool system and I am very happy with them. I am not sure what your extreme cold is, but in New York, teens and 20s are about as cold as it gets.
I have a pair of Lacrosse Alpha Burly boots with the 1500 grams of thinsulate. I love these boots, anything from single digits up to 40 degrees and my feet stay extremely comfortable. Like some have mentioned, make sure you live enough room in your boots to wiggle your toes and circulate the blood better. Another plus is that they are rubber and have no laces to tie up. Hope this helps a little bit.
