Thanks, everyone - the answers you gave were exactly what I needed. If the temps are going to stay in the 20's, I'm going to give the NeoAir a try (and carry that CCF pad, just in case); any colder, and I'll take the Prolite Plus (and CCF.)

I'm still caught in that no-man's land of "lighter is better" v. "there's such a thing as too light for conditions." It's a good place to be caught, though - a much better place than, say, "should I go to work, or stay home and paint the living room."