Thank you all for your initial thoughts.
We installed a CAT6A network at home as part of our first entry into the world of networked music with the mac mini, Naim DAC-V1, NAP140 & PMC DB1I. It has been rock solid from day 1 (beginner's luck, I guess). There's an RJ45 wall socket a couple of metres from the hifi system that we would use. If the streamer needs anything better, then I'll rely on the dealer's expertise.
The NDS is the one to beat and the dealer who supplied our DAC-V1 happens to have a nearly new one in stock...
If only to satisfy my curiosity, there will have to be an NDS vs. DAVE comparison. I have heard a Melco + DAVE at TonyM's house (thank you Tony) but found it relentless & tiring after 20 mins or so. However, the Melco + DAVE's predecessor was fabulous. Worth another try but in our system.
No rush then, but it will be an enjoyable journey. I'll post updates as and when there's something to say.