Hear me out... I would NOT recommend a down sleeping bag in the first place since down looses its insulation when wet. And spending $700 on a sleeping bag that might not keep you warm in a life-threatening situation is a crime.

Let me recommend you all educate yourself a bit on sleeping bags.

First, to the OP, you need to understand that the temperature rating basically means you won't freeze to death at that temp. It doesn't mean you'll be warm. So I would never get only a 0-degree bag unless you never want to use it below 40 degrees.

Do yourself a favor... Read this article on insulation types (Link below). It's biased since it's on the Wiggy's site, but it will do more to quickly educate yourself on important features than perhaps anything else.

I love my Wiggy's Arctic bag. It's not a mummy bag, so there is room at the feet to place my boots and keep them warm. There is no static electricity (which I hate... The cling to clothes). And it will work even if I'm caught in the rain. It pulls out water so well the company sells strips of their insulation you put in your boots to pull water out before you have to use them again the next day. The US Coast Guard puts their gear in their life rafts. One hunter was soaked to the bone and got in his sleeping bag with his wet clothes still on. He slept warmly and the next morning, his clothes were dry.

Down is good because it weighs very little and packs extremely well. If those are your most important characteristics, then it may be best. If you want one to keep you warm, don't get down.