What was the first power cable that you noticed a difference in the sound?

You don’t mention what you have for equipment.

I recently did the same and borrowed 5 different power cables in the $300 range. 

on my mid-level high end system I heard differences for each cable.

the winner then was Pangea 14XL with Cardas copper.

recently someone Facebook turned me on to Ataudio power cables from aliexpress  

here a $60 cable bettered the Pangea 14XL .

so dunno what you have for an audio system or what type of music you listen to  

but if you hear no differences than you will at least save $$.

@riccitone 
Like you I have a Furman now containing only FM tuner and tape deck. Believe I will move streamer and DAC from AudioQuest conditioner back over to Furman and see whether I get similar results. Thanks for the tip! 

Didn't pay much attention to power cords until I tried the AQ Storm Series.  That was a game changer for me.  

My first power cable purchase was a Shunyata Venom HC.  I didn’t hear much of a difference until I improved my system to be much more revealing.  Now I clearly hear the difference between the following cables I demoed; Shunyata, Audioquest and Cardas power cables.  

Shunyata. In fact that's all I use for Power.