Best speaker cables for Harbeth SHL5s

No doubt this has been discussed but...any synergistic recommendations for the Harbeth SHL5s? Electronics are Bryston 4Bsst2, Bryston MP26.

No such thing....borrow as many cables as you can and try them out. You will find the one that suits your preferences/room/equipment/etc., etc.
Ditto the DNM. That's what I use with mine.
Many people, including myself, across multiple forum sites like the Mogami 2921 speaker cable.