My daughter likes the Ibex woolies bottoms as long johns under her daily pants in winter, even to work. They are lightweight but cozy and warm.

That Kahn looks more like a sweater than a 'top'- might be too heavy espec. under a jacket with other base layers.
I have two regular smartwool hoodies that are great when I don't want to carry a hat. They are casual looking. The hoods fit your head exactly, and fit under a bike helmet well. They are different from the sagebrush hoody you link to. The sagebrush is boiled wool (thicker and lightly felted) and does not have the built-in turtleneck that the reg. SW hoodies do. Also looks like maybe the hood is looser and more open?

I tend to layer 2 or 3 wool things in the coldest part of winter. I might start with a SW or Ibex thin base layer top, then a medium weight merino zip turtleneck, then maybe my Shak over that. If it's REALLY cold I might put a heavy felted wool vest over the Shak to top it all off.

If as you say you have quite a few thinner merino tops, try just layering what you have as opposed to buying a heavier top. Perhaps the SW hoodie will round things out for you? Or try the Ibex hooded shak- those are NICE and you could order one size larger so it will fit nicely over your other shak.
Shaks are my most practical items, and I have the half zip and then I might wear the full zip over that, sort of like an old fashioned 'sweater set'.
As for soft and warm- the one most versatile item I own is the SW medium weight zipneck turtleneck in black. It's VERY soft and warm and I have washed mine a hundred times in the washer already....keeps on ticking.
It looks very simple and elegant, so you could wear it at work too, or out to dinner.