My wife just got me a Kelty Cosmo 20 degrees, long down sleeping bag for my birthday. Found it on her own. Won't tell me what she paid for it, obviously, but got it on a good sale with free shipping.
I'd found a previous-year-display-model thermorest on clearance this last fall. Combined with a Cabelas Bivy Bag I bought out of the bargain cave for $39 a few years back I am sitting at 6lbs 4 oz for my all weather sleep kit in a large drybag that I won't be keeping them in as it's too hard to stuff.
The backpack I have is a Wallmart Arrowhead 8.0 bag at 2lbs 2 oz.
I've a polycro tarp I've made for hammock camping I can toss in for extra protection and still be at 9 lbs.
Total cash outlay is somewhere around $250
I am thinking I am going to give it a try this weekend in the back yard. Supposed to be 5 degrees as a low and a 10+mph wind, so I am thinking I may include my wool blankets and bublewrap space blanket for safety sake. Probably will make a topless snow cave with the polycro tarp across the top earlier in the day, and let any snow we get settle on top to help insulate it some. I may tuck some hot-hands into a pocket as well. Just in case.