Class D Amps Cable matter??

Just because interconnects so rarely just start acting up, have you tried cleaning the connections on your amp and pre, or just swapping the interconnects? Worth a shot to possibly save some $, and many report improvements in their system's sound after cleaning connections (including speaker inputs) if you haven't done this recently.

As an aside, are you using any power conditioning? Unlike more conventional amps where conditioning can sometimes do more harm than good, my experience with "digital" amps has been that they sound better with power supplied by a good power conditioner. Anyway, best of luck in sorting out your interconnect issue.

When you swap your Silverstring interconnects between left and right, does the buzz move to the right or does it stay on the left? Wasn't clear if you did that or not. Also, have you swapped your speakers from left to right? If the buzz moves to the right you probably have a speaker problem.