I agree with the assessment. Of all those, the dragonfly black is probably the 'worst' sounding. I didn't much care for the total airhead, either. I really liked the ES-100 and the sound of the BTR5. Just loved the supermacro and kind of grew resentful of apple for doing away with the line level output of the original 30-pin.

As I mentioned in another comment / reply, the apple dongle is kind of the bar for performance and cost. But a favorite? Like all things, it's complicated. The ES-100 sounded great with the 535s. It worked flawlessly, but the battery is just insufficient for long-term use. The BTR5 app isn't anything to brag about, but I really like the sound signature (not so neutral) but I've grown to loathe the battery life and hassle of getting it to work on iOS. The Echo wasn't bad at the time, but couldn't carry around a laptop in your pocket. Strapping on amps like the bithead and the supermacro to your DAP was cumbersome and yet, i'm going back that direction with the ifi Hip Dac 2.

And my age is also a factor. I've lost the ability to really discern the differences between FLAC and MP3 320, especially in 'noisy environments' where I would be listening to portable gear. And after a while, what is the next level of bit rate? Especially on art created and recorded in the tube era or even the 70's? That's not even mentioning really early recordings that I still enjoy.

I do like the dynamics of the original recordings where things were soft and then other things were loud. The crescendos and decrescendos which adds to the adagios and the allegros. The way some singer-song writers used space when they performed. The subtleties of finger picking verses finger tip picks. These days, and all these overly produced, compressed, and remastered recordings just wear me out. It just drones on and on and I feel desensitized, like I need a bigger fix. That's one of the aspects I really like about the balanced verses unbalanced when it comes to outputs on these little guys. Their extra power feels like there's a lot more headroom for turning up those quiet, original recordings.