Speaker cables for NAD C356 and PSB Image B6

I had the older NAD C352 integrated and used the Signal Cable Silver Resolutions. I think it is a very good match, the Resolutions being transparent and neutral. If that is a bit higher than your budget, then you can opt for the Ultra Speaker Cables.
Signal
Cable

I have recently used the JW Audio cables in my second system and for the price, they are awesome.

JW Audio

If these speakers are bi-wire capable, I suggest that you use bi-wires.

I order some Atlas "Equator MK II" spk. cables recently and they are superb. Very pure 6N copper 14ga. Can be order from England for a very reasonable price. I believe it was 5pds. for a Metre. (Bare wire) Shipping was around $10 and arrived in a wk. Really well worth it.

Audioquest or Straight Wire.