You should do a search on fatbikes and snow riding up in alaska. There is a good reason why people use fatbikes for snow riding. A surly pugsly or any other fatbike is as good as it gets, if that doesn't work then nothing else will. If you really want a good snow bike then a Pugsley, Karate monkey or a 1x1 frames are hard to beat ( I have a 1x1 ). These frames are very versatile and can be built up in many different ways.
Personally if I lived in London, Ontario (a snow capital of southern ontario), I would definetly be riding fatbike.