It's a little more than you would like to spend, but I would look at these two bags:

Kelty Lightyear +20:
http://www.rei.com/product/763709

REI Radiant +25:
http://www.rei.com/product/777908

The Kelty has always been a popular and affordable down bag.

The REI is new this year and they are using the EN rating system used by all European sleeping bag companies for increased accuracy.
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