We all backpack in different locations. It would be great if you would define "cold". For me, 40-degrees is warm! 20-degrees expected, particularly shoulder seasons. 0-10 is cold. I have a 5-10 degree bag (but it is a men's bag which makes it a 20-degree bag for me). I get cold in it at about 20-degrees, and that is with the hood all cinched up. Really helps to wrap my down sweater around my neck.

Using a quilt is really not in my future.

My next move for warmer sleeping is a better sleeping pad, probably an R-5 one.