Along the lines of amortizing your bag out is the other question that I didn't see here in your post? What EXACTLY are you using your bag for? 20 degrees sends you past the "typical" seasons, and that would make me ask just how many nights are you going to be out where a true 20 degree bag is needed? If you only do a couple of trips in these shoulder seasons, then you could do with a true 30 degree bag, and then add some clothes to make up for the temps, or an additional pad to insulate better?? I use a 30 degree MH bag, with 800 down fill, and regularly get into the 20's with it. I just add base layer, and a good hat and I'm good to go. Then I have the added benefit of having a really light bag all sumer as well. Worth thinking about! So in summary, really plot exactly how many nights you would need a true 20 degree bag.