I've been fairly impressed with Bridgestone Dueler A/T Revos in the winter. BFG All-Terrain T/As are also not bad, but might be overkill for your truck and the kind of summer driving you're doing. Neither tire is cheap, though.
We run Pirelli Scorpion ATRs on our Suburban in the summer, and have been pretty impressed with their winter performance in those shoulder season snowstorms (like last week). In fact, I'd say they're about as good in the cold and snow as our dedicated Hankook winter tires (which are pretty mediocre, IMO).
As for where to get tires in Canada, try
www.TireTrends.ca (they are - or were? - a site sponsor here). There's also
www.1010tires.com . I've never dealt with 1010, but have placed several orders with TireTrends over the years and would recommend them.