Of course it depends on the size of your personal furnace and how well you fuel it but ...
I made a Momentum + 6oz/yd**2 PL1 + scrim + Momentum quilt and balaclava. It bottoms out at about 25*F (-4*C) when I wear SD down booties, REI Sahara pants, short sleeve synthetic T shirt, long sleeve BSA scout shirt, uninsulated hooded wind breaker and a single ply Smartwool balaclava. I was on an old school 1.5 inch full length thermarest pad. Ground was not frozen.
Add an oversized 3 oz/yd**2 Climashield XP quilt over that and light weight X-Static long underwear tops and bottoms and a full length Ridgerest pad and I'm good to a bit below 0*F (-18*C). This was on snow.
Edit: The two quilt cold weather setup was also in a bivy zipped up to chin level, head exposed. Both situations were under a 5x8 tarp.