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.
128x128fastninja12
@rocray It took me a while to find the VD’s but it paid off. I ended up with 4 total…Im keeping 1 in the event that I upgrade my power amp (my ARC D400MKII has a hard wired pc) I’d love to try the VD on my preamp but there’s no way I can get the bend radius to fit behind my rig, as you know they are ridiculously ridged. 
That is one thing about those cables,they are not very flexible! It took a little bit of effort to get the cable not to move my preamp.  It was definitely worth the effort though. 
I’ll add to the Cullen parade.  These are quite good and the only PC cable I use throughout the system. Crossover ll is his top cable and has stripped down many a competitor.
What is wrong with the power cable that came with the unit?  Dont get on the merry go round.  the best may be what you have.  lol