Class D Amps Cable matter??

What is "acting up"? If you are getting spurious signal, then you might need RFI shielding. If not try the Cable Company lending library which sounds like a great way to buy cable. They let you try it out first in your own system. I would think they can direct you to a cable you may like.

There is a small (about 1 percent) amount of the switching noise on the speaker cables. It can couple to anything else by capacitive or electromagnetic coupling. Capacitive you can reduce by keeping cables away or crossing cables at 90 degrees. Electromagnetic coupling is not very likely since switching frequency is most likely in order of 0.5MHz - equivalent to about 600m wavelength. Antenna becomes very ineffective below 1/10 of the wavelength - 60 meters.

I have Wireworld cables with my Class D Integrated amp. I submit they make a difference.