Furtech Fl-32MR or Qyaide M1 AC/IEC plug ends?

ESL?

The capacity of Humans for self-delusion is apparently unlimited - Mr.Spock

Building a coloring box of $200-300 plugs is quite a commitment.  Are you planning on swapping them one at a time and use the same wire?   That will remove the wire variable but makes it harder to compare the differences back to back.   You might want to think about going with a cheaper power cord wire first and make up a few cables the same design but with just different plugs.   That way it is easier to swap them around and you should hear how the plugs color the sound.
When I hear about power plugs coloring the sound the first thing I think of is the plating on the prongs.  You might want to compare pure copper, silver, rhodium, and gold for starters.    They are all supposed to change the sound.  At least that is what people say.......