I call this The Dishwasher Theory...there's always room for one more plate.
My dedication to this theory drives my wife crazy.

New method: Measure your belongings in terms of weight. We're talking multiple tons per house and probably a ton per room depending on the inhabitants. And now we know the reason for concrete foundations..and wonder why they crack.
standard 40 or 30 degree sleeping bag and puting a a fleese or silk liner in your bag
It's about heat retention. When you're stationary that's done by volume of the material and the materials ability to retain heat in small pockets. Silk is millimeters thick which is nothing. Fleece helps however it has absolutely nothing on three inches of down.
Good camp gear is the equivalent of motorcycle crash gear. A one time payment keeps you safe. And in 2 months you won't even remember the money involved whether you spend $5 on a 60F wallyworld super cheapo junk sleeping bag or $250 on a 0F down bag. The first time you find yourself needing that protection to 10F without expecting it at 2am, you won't be thinking about money at all. You'll either be freezing or warm.