Have you think about an 500W+ AC-DC Adapter to be used with your Dynamo/HDPlex 400w totally passively cooled?
Maybe long enough to fit the S4 MINI or the Dan A4 SFX?
I don't know, but 500W would seem enough for a 8700K and a GTX 1080 Ti.
Just making an idea.
The only AC-DC viable options are...