I believe for end-game audio, EQ is a must, as everyones HRTF is different and you cannot expect to get a headphone that is a perfect match to your HRTF out of the box.
What I am about to say would annoy cause problems elsewhere but this is a science based forum, but endgame audio comes down to your headphone being as smooth as possible in the treble (passed 6kHZ), and then EQing the rest to your preference.
Purchase a Qudelix 5K (this is a powerful, very portable, bluetooth DAC/AMP with DSP, for around 100USD; the biggest bargain in audio) and one of the following IEM's:
1. Moondrop Variations
2. Truthear Nova (with Tripowin Spiral Groove Tips)
3. Simgot EM6L
I have put them in order, starting with the best. Now the difference between 1st and 2nd is perhaps 10-15% in the treble quality, and you do not have to use foam tips with the Variations; if these factors are worth the 5x price difference, then purchase the Moondrop Variations (they are the best). I want to note, you HAVE to use Truthear Nova with 'Tripowin Spiral Groove Foam Tips', as these are the tips that smoothen the treble; I find them very comfortable but of course you may be different. If you do not want to use foam tips and don't want to spend the money on Variations, then the EM6L is an option, but the treble quality is lower than the other 2 options (but still MUCH better than most other IEMs on the market).
Then EQ the IEM's to your personal taste which you can save on the Qudelix 5K, and voila! Endgame IEMs!
I have attached graphs so you can see their frequency response, and also a graph comparing the top 2 recommendations to the AKG N5005 (which, if I am to be honest, is not good, especially in the treble).