I've got a Revelation 20 Deg quilt 6'6" wide; with 30% overstuff. Fits in a Zpacks medium dry sack without too much effort. Zpacks says the medium is "roughly" 6" x12" full dimensions.
The quilt is just 1.1 Oz ripstop and 800 FP down. Seems impossible to fit more insulation into the same size and weight until the invent something that is warmer and more compressible than down. Get the temperature rating you need and I think you can rest assured that that is is going to be as warm, light and compressible as as it gets. Excellent gear.

