Not really a cold sleeper. Also I am a side sleeper so I tend to curl up into a ball when I get cold.
In Jan I tried out a #5 montbell SS down bag, outside, no tent, tarp or cover, heavy dew, 40-45 degrees and I stayed warm.
What I am considering is boosting a 30dF bag to 0 as above. Either that or just carry a MB #1 15dF bag without the quilt.
I already have an older Snowlion -40 bag, which is more like -20 now due to decreased loft, so if I am in constant cold weather in the 0-10dF range I would rather carry that bag, although it does weigh 4#.
The idea behind the combo with a MB 30dF bag is to carry that plus my quilt just in case I hit a night or two where it could dip into the 0dF range so I could save some weight and survive without freezing my ass off.