I'm 6'5" and weigh in at around 115kg now, but been all the way up to 140kg.
Around my area, I have ridden in temps down to -7°C~20°F. We rarely get snow, we mostly get the cold/wet/windy to make things extremely unpleasant. Building up from the base, I always wear a wool top. I have tops with various 'weights' 170/195/240gsm. I'm a sweater too, and the benefit of wool is that it retains heat when it gets wet with sweat. There is no better base layer material IMO for the hot sweater in winter. Over time, I have settled on a wool base (weight depends on just how cold it is) under a standard jersey with roubaix fabric arm warmers. Top that off with a vest and that gets me through most winter rides as I'm a heat generator and can't wear skull caps/beanies because they make me too hot. On the really cold days with bitter wind and/or drizzle/mist, I have a Hincapie softshell jacket that was being run out from Evans cycles for cheap. If it's getting especially wet and I have to ride (eg racing) I have a Hincapie rain jacket that once again I got very cheap. It is made of the event fabric, so especially good.
Hunt around for good quality breathable materials if you're a heat generator like me. I started off with just a cheaper jacket for top layer, but it has no breathability and it just acts like a sauna. I rarely wear it now and could likely get rid of it now I have better stuff. As I said, hunt around, because that Hincapie jacket actually ended up costing me less that the cheapie one!
Oh yeah, and don't forget good gloves!