The capacitance element of your current speaker cables may be more of a contributor to the amps running hot than the resistance.
It causes the amp to oscillate - sometimes to the point of distruction. It used to be documented on the NAIM web site as something to avoid. It’s also something that many high current designs suffer from. I’ve encountered it with a friends Ayre amp also
I have a Naim 5i (mkII) and it has never run hotter than room temperature (i.e. cool to the touch) with any of the cables listed below
I’ve used Van den Hul CS-122 and D-352 with great results. The Magnum also looks like a good choice
For even better results i separated the two conductors with a minimum 1-2 inch air gap. The improvements in clarity and imaging were very noticeable
Also try Furez silver plated copper terminations with the VDH cables - they work exceptionally well
http://www.douglasconnection.com/Furez-Products_c20.htmI now use gZero6 from KLE Innovations, but they have a 5 meter limit on length, but I would give them a call to see if they can do anything - superb cables
Hope that helps