I have two down parkas and a light synthetic vest. The parkas are for either extremely cold weather or moderately cold weather. I wear a long Capilene midweight base layer and a light fleece jacket much of the time in cold weather, then put on the parka when I stop or in the evening.

The big parka gets little use. If your temps are in the teens, something like a TNF Nuptse (what I have), should be fine. It doesn't have an insulated hood, which would be nice, but I have hats for that.

My vest isn't very heavy duty, so I just use it in slightly cold weather. I like having my arms covered, but it adds a bit of warmth if I am out walking at night.

If you are sitting around all day, I would think a parka would be what you'd want. Otherwise, your arms and shoulders are likely to get cold.