I found it. Here is are the Naim solutions:
You’ll need cable 5 here. One made for NSC222 to NAP250DR. The Atom HE has the same connectors.
So what I said above is not entirely correct. The RCA puts on the HE is not the suggested. Here it is double XLR for HE into single XLR for 250DR. But as the amp is unbalanced I doubt that there would be a difference between the two options.