Speaker cable for Nad 7050 and KEF LS50

It's simply personal preference. QED is a quality cable, that some listeners like and some do not.

It appears that your cables are very respectable. My only comment is that QED is silver plated copper and you may find that a stranded copper conductor may have a warmer presentation. Or a single copper conductor such as Audioquest may be more to your liking.

You need to decide what kind of change, if any, you are looking for. Most will say that cables should be transparent, but in reality certain cables may colour your system in a desirable way.

And with cable selection, it's trial and error to find which is best for you.

QED with LS50 is a recipe for bleeding ears.