I saw an article recently that said that the whole "put a hat on" theory wasn't true, except maybe for babies-has to to with surface area compared to overall body mass. I like hats anyway, so I'd be wearing one.

I have a pair of insulated pants. Mine are not down, not sure what they are. Got them from GoLite a few years ago on a closeout. Full side zip and pretty warm. Those plus my big parka and I can sit around in +15-20F and not get cold at all. As you can see from my pics, I use pieces of a blue pad for sitting or standing on. Plus I have a pair of down booties. I might get one of those rabbit fur trooper hats too.