Patrick,

If you go to my thread entitled "My quest for the ultimate winter cycling shoe" , I discuss some methods for dealing with this that I intend to try out. Read the last three or four posts regarding the aerogel insoles.

One other thing that I seem to have noticed is that carbon fiber soled shoes are warmer than plastic soled shoes because the carbonfiber/epoxy composite material does not conduct heat as well as hard plastics. Unfortunately none of the current crop of winter cycling shoes use carbon fiber soles which would add to their cost.

One of the reviews of the Specialized Defrosters lamented the fact that they just were not warm enough. So if you have enough room for an aerogel insole that should improve matters to some degree.