As for which cable to replace first, buy one cable and move it around. See which component improves most. Buy a second cable and repeat.
Help selecting a power cord.
All my gear has the factory supplied power cords I’m ready to try 1 aftermarket power cable as a test. So what brand power cable should it be and what device gets it first? Tube pre? Tube main? D/A? CD transport? Roon Nucleus? Subs? GE Trefs?? Turntable? Oppo 103? Which piece of my gear should be most affected by the improved power cord?? I look forward to the responses and will likely choose the cord that has the most recommendations.