Depending on the situation there is wide range to chose from. Even as a hot sleeper I would not recommend any bad rated over 32 degrees. If its hot, your hot no matter what your in or not in. If its chilly or cold, i like 32 at the min and then working down.

FEATHERED FRIENDS, in Seattle is by far the best sleeping bag I have EVER seen. They routinely outfit peak and antarctic expeditions.

Mountain Hardware is also very good.

I personally use Big Agnes. They are middle of the road as far as price and manufacturing. They cut weight on their bags by taking loft out of the bottom off the bag and including an insert for a sleeping pad. This way the bag is lighter and it never slips out off the pad. The pad is in it.