Yeah I'd definately look at a better rated bag. I've slept in low 40 degree weather in a cheap 40 degree rectangular Kelty bag and it was bearable. A decent mummy bag should easily handle that temperature. Besides the well-known quality brands, don't overlook the Coleman Exponent line. It's not the usual Wal-Mart level of Coleman quality, but something competitive with the better backpacking brands at a lower price. Not a market leader, but they're a bargain if you don't mind a little more weight.