The listener is the biggest factor though. Having speakers or headphones that allow difference to be heard doesn't guarantee the listener will hear those differences.
There have been a few times where people over the last few years, were recommended better audio gear than what they were using at the time, but noticed little to no difference.
One guy who ended up buying Q Acoustics 2020i and a Marantz amp after recommendations, didn't think the sound was as good as his £50 Logitech 2.1 speakers.
I remember another guy on a different forum, who noticed no difference between a X-Fi Titanium HD, Xonar Essence STX and onboard audio. I forget what the headphones were, but at the time I was surprised as they were pretty decent and should allow at least the difference between the sound cards and onboard audio to be heard.
Admittedly, those two examples are quite extreme.
There was another member of these forums, who heard no difference between a Chord Mojo and SMSL Sanskrit. He has Naim amp and Rega speakers IIRC.
Some people's hearing is better than others. Some can discern details and hear flaws more easily than others.
Probably a good thing not to be able to hear the differences between DACs and amps. Will save a lot of money.
