like spinfit w1/cp155/145 or divinus velvet

ye I use spinfits, dunus double flange tips, fiios double flange tips, fiio foam tips, dunu foam tips(my favourite most of the time but I can’t wear it with wire nozzle stuff, it puts to much pressure to my ear canals) but those won’t make it any narrower if he wants something narrower, that was my point, spinfits you can wear shallower and I could see that helping tho

Zero Red have wide nozzle, you won’t get anything noticeably smaller than small tips they give you, if they don’t fit look for different IEMs :/

I’ve had both CHU and CHU II, CHU II sound much better but they are both very uncomfortable for me too, I am sensitive to 3kHz frequency most chi-fi brands love to emphasize, my current go-to IEMs are CVJ Mirror, they used to be $98 when they came out in 2021 but you can get them for ~$45 these days, sound completely different from CHU(II) and fits me much better, nozzle is a bit wide so I prefer different tips than compared to some other IEMs I used in the past

Moondrop over-ear stuff got great cables, I also quite like Thieaudio Ghost cable, quite unique, not sure how durable that will be

so if the headphone power calculator

problem with it is that it calculates based on 1000Hz impedance, not on highest impedance peak you should be calculating with, HD800s is rated at 430 Ohm at 1000Hz and it uses that number instead of it’s 680 Ohm peak at 93Hz

also some amps low gain modes are done properly, some are just high gain with pre-amp basically, very lazy approach, low gain should be more linear, if your AMP can’t give same amount of power(mW) on lowest impedance drop and highest impedance peak it will change the sound, how much it will change it depends on how big the difference is, all the good sennheiser and beyerdynamic stuff are famous for this, HD800s you might realistically be able to overcome impedance peaks with a powerful amp, but some things just won’t happen like T1 which peaks at 1400Ohm at one point and it will sound different on every amp

tldr:/ I would only consider that calculator to be 100% correct for planar stuff because they have VERY flat impedance curves, very rarely some $1800+ dynamic driver headphones also have flat impedance curves like Sony MDR-Z1R

you would hear a difference with a much better AMP, with a bit better AMP probably not, if it’s plenty loud already you can apply negative pre-AMP and just EQ them a bit for that usually 80-100Hz dip in Sennheisers you get with lack of power because of increased impedance, HD800s also have a bit of a 70Hz dip so instead of applying +2dB on 90Hz like usual I’d apply it to 85Hz

IE200 have absolutely awful cable and you can’t change it because it’s modifier mmcx, so standard ones won’t work, you gotta spend another $100 to get their own upgrade cable, if you don’t mind a bit of BA timbre from relatively cheap hybrids go with Truthear Hexa, basically on par with Moondrop KATO but hybrid instead of single DD so you get a bit of that BA timbre, otherwise matches 1:1 to KATO in everything and KATO is a very good $189 IEM one of price point defining IEMs