Runrunsmithfly
Previously known as ssmith3046
Why pretend?You're looking at this the wrong way. You should be looking to get to hear better gear that makes the iFi Diablo sound average. Hearing a variety of that better gear is the style and level of sound quality that may get you to hear that amps do have sound quality differences, and can in fact have significant sound quality differences once you get to hear the really good stuff.
Do you have any headphone meets in your area where people bring some high-end gear you can try?
It was going to headphone meets 12-15 years ago where I got to hear some really good gear that got me to realize that wow I didn't know headphones and amps could sound this good and have this much headstage and this much imaging and this much musical enjoyment. It was those meets that got me to realize I need to chase that level of headphone sound quality, but somehow do it for less money. I got to hear a variety of really good headphone systems. Some solid state, some tube, some with NOS DACs and some with oversampling DACs (like Benchmark and Berkeley Alpha). You need to get to hear more than just the iFi Diablo to understand and experience what the better headphone gear does and how good it can sound.
Once you hear a variety of the better higher-end gear you'll be in a better position to hear what the difference are between high gain and low gain with the Piety.
When listening to high gain and low gain with the Piety you should be listening for the sense of space in the headstage, the sense of density in the sound and music, the sense of punch in the transients, and the sense of space around instruments in the mix. And things like that. Pretend you're stoned and listening, really listening, into the space in the recording and the feeling of the sound. That's when you'll start hearing what's different between high gain and low gain.