What I feel is useful information in choosing a jacket:

The best winter cycling jackets | road.cc

You need a surprisingly minimal amount of under layers with a soft shell. My record with one was a -15 Fahrenheit ride into work, and if I recall correctly I wore a thermal undershirt with two summer jerseys over it. Worked fine. You can ride comfortably with just a thermal under layer a lot of the time- or even just a summer jersey.