Thing is with socks, is that if you get thicker socks you get whats called hot foot and cramps, use your normal socks and get a boot protector which cuts out the wind and grime and just fits snuggly over your riding shoes and comes in various heights to suit.
They have holes cut out for cleats and heels etc and are quick and easy to take off.
Also, if you wear Merino socks they help with keeping warm but general cycling socks are the best, remember we loosa almost as much moisture/sweat/heat via our feet as we do from our head. If you ride a lot its may also be good to have 2 pairs of shoes, that gives the leather/material time to breathe and cool/dry and greatly extends the life of the shoes, this also goes for everyday shoes.
A good mate in germany is a master shoe maker, quite amazing how much shoes can tell about a person.
If your requirements are to buy today.............
Go to Bicycle Express............
Either way, don't forget a colour scheme that matches your bike and attire :)
De-Feet Woolie Boolies. They're woollen cycling socks.
Sealskinz. Waterproof and warm!
If you dont want to spend money on shoe covers just get an old pair of sox, cut a hole in the bottom for your cleats and pull them over your shoes. Its amazing how much warmer your feet can be just with something as simple as that. I used old cotton sports sox for years
+1, They are a bit thicker though so dont purchase if your shoes are already a little on the tight side. They are nice and soft and comfy. I may look at getting Sealskinz (also thicker) this year for when it gets seriously wet, that way I'll have the best of both worlds - cold weather and we tweather socks. Im not sure if you can buy either of them near to home though :-(
I bought some Pro H2O covers last week from BE. My feet are now very toasty wearing the same socks I'm comfortable wearing in summer. The benefit is if you feet get hot, you can take em off, cant really do that with socks.
Icebreaker make some nice bike merino socks
Merino sock by Icebreaker. Go to Mountain Designs on Rundle St and they might still have a 2 for 1 deal. They have a specific cycling sock but I can't tell the difference between that and a walking sock.
I do agree you need boot covers, preferably waterproof.
+1 for Icebreaker socks. Warm but not too bulky and comfy too.
I just use two pair of bike socks and boot protectors they dont look great but they work well
Here's a tight-arsed approach that worked well for me last year on several winter rides:
slip a freezer bag over your toes when you put your shoes on!