Is it just me or should the items you listed you already have keep you warm in the teens say 15F + or - a few. I have never seen, or handled any kuiu gear, but EVERY single person i have ever seen talk about them is always cold. Is it a coincidence?, i don't know, but its definitely starting to make me think twice about buying kuiu clothing. It seems every place i hear it its with people that have the 185 and 250 baselayers and the guide jackets. Would like to handle some of their stuff first hand someday, but at this rate not sure if i will ever take that leap of faith. I am REALLY not meaning to bash kuiu here, just IMO 1+1 is not =2 in this case, something just isnt adding up.
Anyways, I have a pantagonia nano puff and agree that it is an awesome piece of gear. IF you can't stay warm with a nano layered in down to 0-5F or so then there is definitely something wrong with the other items. Especially if the rest of your body is properly clothed with hats, gloves, long johns etc.
Do those guide jackets/vest really block the wind? That can be the only thing i can think of that would render them less efficient.
For comparison sake this is what i wear down to -30F with absolutely 0 issues, layering the items as needed.
Head: smartwool beanie, balaclava, hood from an old hunting jacket
Torso:capaline 3 l/s, UA 1/4zip mid weight heat gear, WW2 british army wool sweater, pantagonia nano puff pullover, ECWCS goretex parka w/o liner
Hands: marmot wrist gaiters, smart wool glove liners, EMS fleece fingerless/mitten combo, OR endeavor mitts
Legs: capaline 2, winter weight bdus, cabelas down pants/long johns, ECWCS goretex pants
Feet: wool hiking sock, wool mountaineering sock, insulated boots, OR croc gaiters
For my torso, i am down to the teens with the capaline and the UA, and either the sweater OR the nano, never need both. I only add in the parka shell when its raining or REALLY windy.