You've got a good start with those boots. I have a pair of Sorels also, although they're about 30 years older than those! Great boots, just won't wear out - just need to replace the felt liners once in awhile.
Speaking of felt liners - consider getting an additional felt insole, preferably one with reflective foil on one side. Put that in, foil side down. Hopefully, you won't make the boot too large to get the regular liners, plus your foot and sock (and a very thin breadbag). Assuming, of course, that the Sorels have removable liners.
Also - consider getting a backup pair of liners, and swapping them out in mid-afternoon.
And, don't overlook chemical footwarmers. The handwarmers will work, but they're a little thick and will cause your toes to curl a bit. Probably not a problem snowmobiling, but may throw you off if you use them hiking. If all else fails, you can get them in a ski shop. Don't put them next to your skin, though - they may burn it. Put AT LEAST one sock layer between you and the pad. And, it takes about an hour for them to come up to temp, so put them in while you can still feel your toes.
And, in way of emphasis - get a pair of SmartWool sock liners. A bit too warm for summer, but winter - they can make a HUGE difference.
And yes, I know a little something about cold feet. Among other things, I ran the main Killington (VT) chairlift on weekends/holidays when I was HS and later college vacations, and I once climbed Algonquin (NY ADK's) when it was -44F. That's not windchill - that was the still-air temp. And yes, I frostbit my toes, mainly my right foot. It's still sensitive.
Edit - you probably know this already, but ... besides a helmet, what are you wearing on your head & face? There's an old saying - if your feet are cold, put on a hat. Most of our heat loss is via our head.
Last edited by KevinR; 01/03/11 05:36 PM.