I have the Kuiu Attack pant and while nice, they're pretty form fitting unless you size up quite a bit. So as an outer layer, they could get snug quick. And they're not windproof, so you'd notice a good breeze I'd say. I can get one or two base layers under them, but doesn't keep me warm all day if temps are in that 20-30 degree range or lower. I have a buddy with the Fanatic Lite bibs and they seem to allow for more layers beneath, depending on body type of course. You could wear a rain pant or wind proof pant under the bibs if you by chance already have that and want to cut down on cost/buy more stuff. You could get the Attack Pant on sale and use those most of the season, then on cold days carry in some decent Gore-tex bibs for windproof and waterproof. Too many options. ha!
Oh and the Fanatic Lite jacket is quiet and I wanted to love it, but I couldn't layer under it enough for cold archery sits. It got too snug in the arms. Sitka and Kuiu are made really well, but they come as a set/system to make you buy more of their stuff. Smart, no doubt. Just depends how many layers you want to wear under them. I tried the Kuiu Guide Jacket, same problem with layering, returned it. But if quiet is your main goal, Sitka gets the nod.