Which wire has biggest impact?/

The wire in the fuse. It’s big. Big big. Bigger than big! 

When I first got into cables I remember switching from the top of the line Monster Cable speaker wire to Furez 12AWG cable on a pair of Legacy speakers.  Furez speaker wire only run $1-$2 per foot.  The difference in clarity and extension blew my mind, it was not subtle.  I've been a believe ever since

slap a turbo on it.

None of the above.

Digital coaxial cables are SO different from one another that I can make my system sound VERY different by using any of the three that I own. Each has its own virtues and shortcomings.