All of these are easy to drive for the RME up to ear-bleeding volumes..
Sounds more like another one that missed the High Power setting...
I turned it on, it was just missing something out of the quarter inch.. I plugged them in a phonitor (phonitor was powered by the rme adi-2 dac) and it drove it better, stronger more dynamic, to me a clear winner as far as power and clean goes, superior to the rme adi-2 dac Amp side (quarter inch) for iem I prefer rme.
I love the rme dac, sound quality DSP, vast features and pleasant screen. It was no slouch but I would say the phonitor, strickly looking at sound quality out of the quarter inch out was about 30/40 percent better than the rme... I'm a big fan, but I have to give credit where credit is due.
High power setting was turned on. Listened in SD sharp and slow, after initial thoughts on eq off I did eq on just to fool around and the rme did a great job as usual and the headphones responded well to minor eq changes as well.
Loved it all, but the clears were bright, the ethers not so much, going to skip utopia out of the rme, and just get the stellia.
Remember, amp is not solely about just driving something to Loud volumes. A 50$ amp can do all that.... But it is the *authority * or energy it can drive it with, more of an effortless sound, on caffeine... Ect.