Your first part describes the Df, but quiet isn't what comes to mind compared to some other choices:
https://www.youtube.com/watch?v=PcXG3AH0lf8
Do you really need to use the legacy glass? Often times it isn't as good as you remember. At this point, Sony is making serious strides and Canikon should be nervous. The new A7r2 is pretty ridiculous. And you can adapt your old Nikon lenses.
Many still pro shooters are increasingly shooting video so you might want that to be a more important criterion.
The dSLR is increasingly losing relevance for all but niche shooters.