I'll agree the Kelvin WS down puffy is amazing...really shines when the wind gets going. What's it have , 5.5 oz of 850? Not sure.
Probably not on par with feathered friends , western mountaineering, goose foot, etc tho. They have several levels above the Kelvin. I didn't pay full price for the sitka and for that money I'd look at some of the above boutique options.
You are missing the best glassing puffy jackets, which are from non-hunting brands. Tons of threads on them here if you do a search.