Athleticum recently had a sale on Columbia Bugaboo2's for around 70 francs. I bought a pair and I am pretty happy with them.
I wear a US size 12 (47 euro), which is about as big as you can buy without having to go to a store for freaks. I was a little worried about them being a pain in the butt while driving as far as them being a bit clumsy with the clutch, but they work fine.
If I leave the top two eyelets untied, they are easy to slip on and off while changing to ski boots at my car.
They are warm enough for anywhere in Switzerland as long as you are doing any sort of activity, and have good traction.
I grew up in northern Minnesota, and I don't think these would be my choice for spending all day on a frozen lake ice fishing with temperatures down to -50.

Sorel Caribou's are a good warm boot, but they are very clunky and I would not recommend them if you are looking for a pair you can drive with. They also have a fleece top that may look sexy, but has a tendency to collect snow if you walk in the deep stuff. But if warmth is your only criteria, Sorel's are the way to go.