I have a Phillips Fidelio X2. I've used it with my Ipad Pro 10.5 (2017) for listening to music on Spotify for a long time. Because of its low impedance, I never need a DAC/Amp for a decent loudness.
Honestly, when I use another pair of IEMs, Sony MH750, which is much cheaper than Fidelio X2, I couldn't distinguish their sound quality or realize any significant improvement. Now when I decide to invest in a new pair of IEMs about 200-300$, I'm really confused whether I need to pay attention to a DAC/Amp also. Because I don't plan to bring the DAC/Amp everywhere, I'll probably choose low-impedance ones.