14 years ago my wife and I geared up for ultra light back packing. Our guild was the Back packing light web sight.
We purchased Bozeman Mountain works Arc X down Quilts that weighed in at 16 oz each and had a comfort range of 32 to 60 degrees.
We later sent them back to Nunatak to have them over stuffed by 2 oz each, making them weigh 18 oz.
Down quilts work as a system. You need a good insolated mattress and a layered clothing system to wear in the quilt when it really gets cold.
I like the Big Agnes Insolated Air Core sleeping pads, they are light, pack small and are comfortable.
The Nunatak Arc Alpinist is the top of the line.
Jacks-R-Better sells an line of quality down quilts for less money.
Once I started using the quilt system I never looked back. I have one of each the 18 oz Arc X and a Jacks-R-Better 29 oz winter only quilt.
These items come up for sale on EBay and back packer classifieds from time to time.
You can research the ultra light forums for gear reports that will give you a good idea of what will work for you and at what cost.