Welcome - below is a link from the FAQ category which details the technical specs of NACA5 and emphasises the considerations in play. Naim amps of late have become more tolerant of other brands of speaker cable but as Richard points out using a not well-matched cable can bring performance/sound issues and not do the amp any favours, especially with the older ranges. I find NACA5 very ‘fast’ and it delivers the famed Naim PRaT in spades but at the expense (relative to some others) of detailing. The rub is that all cables have their own qualities and some Chord cables I’ve dem’ed did some undesirous things to the bass and the PRaT of my system.
The 140 is a wonderful amp and I would stick with the NACA4/5, as it was designed to work with these cables.