Your main issue is going to be the amp, not the dac. Apple dongle has a fairly decent dac in it, but not a whole bunch of power. With IEMs and a lot of headphones you don’t need a super powerful amp so something small and portable that can also be used at the desk is what I would recommend. BTR7, Hip dac, topping g5, and you’re set for good honestly. If you want to go cheaper, there are several good portable options around $100, and if you don’t care about portability, a $100 amp would probably be just fine for you. It all depends on your needs really.

I have a IEMagni and Modi 3+, but I find that for most situations, my Corsair wave xlr interface works fine and there’s not a whole bunch of difference as long as I’m not critically listening. It takes up less space and I can monitor my mic at the same time too. I primarily use my headphones at my desk and game a lot and talk in discord so the interface works best for me. Though I find myself really wanting one of those portable dac amps I mentioned so I can listen to music in other parts of the house. Your use case may be different though.