Hang around here a bit more @Cosca , this thread is ‘quiet’, even restrained, compared to some
The issue at hand:
1- If you haven’t looked at this already, I’d suggest you check this link on this 'site:
Speaker Cable for Naim power amplifiers - Frequently Asked Questions - Naim Audio - Community
Be mindful of twisted cables - and it seems some manufacturers don’t state the specifications of their cables.
2- How long do your speaker cables need to be?
3- a good starting point with Naim is to use NACA5, as it’s ‘fast’ and relatively inexpensive but not greatly detailed when compared to others. With a (superb & highly revealing and ‘efficient’ in power terms) Focal Be tweeter on the end of it, it can sound bright/perhaps edgy. The Tellurium cables tend to offer greater detail to my ears and take the edge off the top-end of the sound - but some are expensive e.g. the Ultra-Black.
A regards your speakers and kit, the key question and aspect for consideration is whether your speakers fit to your listening environment very well (they obviously do per your post), with the sub-set question of do you want to improve the system further down the line? - which, given the cost of the speakers, suggests there could be more spend to come? If you haven’t already worked it out, this is a place where it’s very easy to spend another person’s money!!!
The great thing is that you have a speaker where the replay can be improved/upgraded quite significantly – and the only ears which count here are yours.
As others have said, the orthodoxy is usually to spend more on the source(s) and amplifier(s) - that is, information which isn’t originated/extracted from/by a source component cannot be recovered down the chain of replay. Better source = better replay.
This is all relative, in that what you’ve got sounds good to you, but please be assured there’s more that can be delivered from the Focals.