For 'hearing a difference'.... First off, there is a threshold ofr quality of the whole system to be able to begin to hear small differences. As the quality of the total system increases.. it gets easier to hear changes due to wires.
For example. Back in the 2000's I owned equipment costing like a few hundred to $1000 to $2000. And the first time I heard any difference was with a power cord I bought (ONLY because it was cheaper than I could make! An AC9 Pangea, when they first came out, cheap!!) and discovered to my AMAZEMENT with it on the Forte 4A amp I owned The bass was tighter and 'better' to a small but hearable amount. with that cord on the amp than the OEM one. First time I heard a difference! Prior to that I did not have any 'belief' that one could hear a difference.
In 2010 I retired, and spent a pile of money upgrading a few bits to typical $5000 a pop. Speakers, amp, preamp.. Plus I added a power conditioner. After those items I realized I could hear differences in interconnects too. Not huge differences, more like the same little changes I heard in that first powercord, but also noting less grunge in the treble, greater clarity. And I bought more Pangea powercords. Low priced ones. but still aftermarket.
After five years I decided to try some better IC, and went for then new Cardas Parsec. I liked them in general, but the one long one I would need (7meter) from the gap from pre to amp sounded not very good. Well it took me another few years to just jump in the deep end of the IC pool and bought ONE $3200 pair of IC for the 7 meter pair. and was a good sounding choice. So I bought a few more of the same sort for the shorter runs (Kimber KS 1016, KS 1116) For the huge price the difference was tiny, but I was thinking of the future upgrades... (clearly by then I became a 'believer')
Get to last year, 2018, I did major upgrades to speakers, source. To Magnepan 20.7 speakers (without which I doubt I would be able to hear a lot of what I can now hear from the wires etc) and from a used $250 DAC to a $7000 DAC which after auditioning at home for five days, really is better enough to float the cost. (I probably would not have heard the difference without the $13,850 speakers!).
Then on a lark, and because they were on sale, I bought a few Furutech duplex. GTX-D Two gold, one Rhodium NCF. Well they made a big positive difference! over the basic Pass & Seymour I had used. Clarity, better sounding right off. So I bought a few more, and over two months bought 17 of them, and even put them into the two power conditioners.. This is were suddenly I can hear changes as small as swapping a power cord from a gold to a rhodium AC duplex. Differences in $200 power cords.
And then (also because in sale) I bought a few PS Audio noise Harvesters, They did some good, bought more. total of seven now. Borrowed a noise sniffer from local dealer, and worked out what is adding noise... (there is a post here somewhere about it) and got even better sound.
The latest I can hear subtle changes from tiny adjustments to the Magnepan 20.7 midrange resistors.. Plus differences in quality of the resistors.
All that to just say it takes a level of quality in the gear to really be able to hear the differences in wires.