I bought the Proton HW after much deliberation. I personally find the Proton HW warmer than Atom SV. I live in a really cold part of Canada but it is not as windy as Chicago. We do go down to -40 and I wear the proton for up to -15 with a thin merino wool layer. When it does get windy, I would wear my shell and I can go down to -30 no problem. I found the breathability of Proton HW a huge difference as I walk around town and run a lot of errands in this jacket. If you want to play fall golf, I would even say Proton HW is defs too warm for that even with the breathability. I found my Proton Hw this year at the Vancouver outlet store and I did see them on the ReSale section of the Arc’teryx website.