Hifiman Sundara - Usage at home on my desktop
Hifiman HE-R9 - when I want hard hitting bass and don't feel like wearing my sundara
Anker Sound core A40 - when I out on the go, or using my phone docked into my gamesir X2 controller. Playing a game otg or on the excise bike.
ER2SE - When I'm on my laptop listening to music etc
I have an Fiio M7 and when I got it, it was worth it for me because at the time I had an iPhone 12 64GB, so I used the M7 for portable music player with a 512GB micro-SD. Since the phone space was too small for my music library.
But since I upgraded phones to a galaxy A53, I don't really use my M7 anymore, due to the A53 having a micro-SD slot. It is something different if I switched to a phone without one, as I would still be using the M7.
So, it really depends on you wants and needs really.