Also, as a weight comparison, the high-end zero-degree down bags my wife and I have weigh 3 lbs, and they are much closer to a "true" rating. In cold weather, I'd expect the zero-degree down bags we have to keep us warm more effectively than these "-20 rated" ALPS bags. And weigh less than half as much, and pack a lot smaller.
I'm not trying to be snobby... I'm just saying that if you're planning on hiking any distance, DON'T get this bag. You'd be better off watching craigslist or Geartrade for a great deal on a lightly-used bag.
The other thing I'll say about high-end bags is that they don't loose a lot of value. If you can get a lightly used bag at 60-70% off retail, you'll be able to use it for a year or two and probably resell it without taking a loss... maybe even make a small profit.
When you're going to be more than a mile or two from the car, I'm a big believer in having the right gear for the weather you'll be in. Nothing makes a trip more miserable than having wrong gear and poor knowledge. It's uncomfortable and potentially dangerous ... especially at these temps.