Winter/Shoulder season Sleeping Bag

I am looking at Down Sleeping bags for winter backpacking and mountaineering. And the shoulder seasons.

At first when I was looking at Down Bag, my Criteria: 2.8lbs or less, Temp rating of 0-20 and under $300.

This was extremely hard to find. Then I came across EMS Sleeping bags.I have a coupon to bring it down to the prices that I listed. But the question is Temp rating of 0 or 20? What are the pro's and con's?

Both- 750 Down Fill, water resistant, Mummy, Stuff sack included.

The 0 Rated Bag- 3lbs. 8 oz Price $271.20

The 20 Rated Bag- 2lbs 3oz Price $191.20

I know I could use something like a Sea to Summit Liner to add warmth and put the sleeping bag in a bivy to increase warmth as well. I'm leaning towards the 20 F bag in terms of weight and price. The only other bag that I can find that comes close to this criteria (weight and price) is the Marmot Sawtooth 15F $183 Regular length, weight 2lbs 14oz, 600 Fill.

Location: NH, below treeline
Temp: 0-35F+
Sleep: Warm Sleeper

Advice? Suggestions?