For temps into the 20's (I've not had a chance to test this system, so I don't know how low I could actually go):

HH Explorer Asym
MacCat DeLuxe Tarp

Outside
JRB Nest as Underquilt
Homemade Gray Ghost as Underquilt
JRB Weathershield

Inside
20 degree Kelty mummy bag as quilt
CCF pad (if needed)

Clothing That I Would Wear
Polypro Long johns
Wool Socks
Grandma Hat
Fleece Pants and Sweater (if needed)