Stronk
Herald
Ayy congrats dude! I got my first open back recently (Hifiman HE400i) as well and I'm loving them to bits like you. Exactly the same impression - the instrument separation, details and soundstage is magical!I got a used HD599 SE earlier today. This is something else. I have never had headphone this good. The level of details and instrument separation is damn good. Even busy songs don't sound like a lump of sound.
The volume is fine on an iPhone. This is my first open back and I absolutely love this.
If and when you can, I'd recommend getting some lossless files (preferably 24bit) and a decent DAC, trust me they will sound even better with them! And welcome to the rabbit hole haha, it's quite a slippery slope from here on XD