i don't have winter shoes, but i never have a problem with cold feet, and i am typically walking around my house with cold feet and hands no matter what the temp is outside. so i wear a very thin synthetic liner sock and smartwools - the medium thickness, for hiking (but not the light hiking version).
i think more than just avoiding sweat (that's really important), you have to make sure that there is some space for your feet in your shoes (not like huge air pockets, but 'space'). if you put on a real heavy sock and put your foot in a really tight shoe, you're going to have temp probs with your feet no matter how warm the shoes or socks.
i have specialized shoes that are webbed (and very 'holy' might i add - they are great for summer riding), and i rode this past sunday at allamuchy with temps in the teens without a problem for 2.5 hours. i made sure that my velcro and straps were a little looser than normal. but if i dip into a stream crossing - that'll be a very bad and different story (but i carry two zip lock bags and extra socks in my bag - the zip goes around the fresh socks in the wet shoe in case of a sub-zero foot dip into a stream).
kinda like fitting a ski boot - snug is good - tight is bad when its cold (IMHO).