Where I live in NY is just a stone's throw from the NY/CT border, in fact one of my favorite local places to hike and camp would be at Bulls Bridge near Kent.
My own standard for winter camping around here is 0F rating, and for the ADK -30 I don't think you can "go wrong" with either plan, I guess it depends how much you plan to use the UQ for fairer-weather backpacking. Using the 3-season supplemented with a pad or perhaps an IX-insert should work in the cold, but will be lighter and more compact when it's less cold.
After reading and reading, research and researching on these forums I finally just decided to go with a UQ/TQ. Last few outings in the fall sleeping was just too cold and I felt trapped in a sleeping bag. Went through a few of those along the way, just never found one that didn't make me feel confined. Bought a 3 season set up from hammockgear and should arrive this week. Hope to test it soon before my spring hikes start.
Yes if you add more down it will lower the low temp rating, not sure on how much down is needed though to make a difference, also not sure at the point when you are not benefiting as the baffle height would need to be increased to gain the needed loft!
Clear as mud?
"yesterday is history, tomorrow is a mystery, but today is a gift---thats why its called a present" - Master Oogway
It's always best if your an early riser!