A down jacket and a lightweight rain layer are a must for me - pretty much regardless of time of year. They serve as a safety net and will save your butt if things go south. When I hunt in below freezing temperatures (especially when I will be doing a lot of sitting), down pants are a must as well.
As far as the meta, pick your poison. Research the amount and quality of down fill in garments before you pull the trigger because they are pretty darned expensive. I have a Kuiu Superdown Pro set, but they are really not what I would consider warm garments for cold temperatures. Stone Glacier's puffys are too fragile for me. If you want true cold weather protection, consider Feathered Friends options (Volant and Khumbu) that are made for the climbing community (think 8,000 meter folks).
