NS,
Just my humble experience, but if I'm moving, a short wool T over a long wool T, a vest with one layer of Climashield, a fleece cap and a windbreaker will take care of me to about into the low teens. Things are different if you are sitting around in camp. If I'm UL, I just wrap up in my quilt. Otherwise, going heavy, a full insulated jacket is real nice. But, hey, that's just me.