AKG - K701

I will say AKG K701 great sounding cans, the cons: open ones (no much Isolation, in and out) and they need power... not necessarily bestial tube audiophile amps but not cheap DAP direct out.

AKG 701s, Sennheiser HD 599s, Apple AirPods Max, Apple AirPods Pro 2s, Sony MDR-M1s, BeyerDynamic 990s, Audio-Technica AUD ATHR70X, nothing terribly special, but decent. The A50s sound exceptional to me.

Headsets are often very overrated. Separate headphone and mic are far superior and often cheaper as a combo too. And you can swap out either, whenever. Beyer is great as people said, but personally I use AKGs (K701 and K545) for headphones, and some cheapo Trust (Netherlands) mic but it's still much better than non-standalone mics. *AKG is Austrian and used to be made in Austria, but now made in China. Idk what to think of their new headphones tho (mine are 12+ years old), but I hear they have excellent mics.

I had a slightly higher budget but got the same problem. My suggestion is to open 2 tabs in the browser: one on your preferred shop and one on autoeq. Autoeq is the most amazing free (open source) collection of professionaly measured headphones. Get the cheapest overear (usually closed) you can find in the shop and in autoeq. Then let your brother use autoeq to get the settings to linearise headphones even more. People recommend sennhaiser? If the model is in autoeq go for them, they become flat for free. I did this with a pair of akg k701. https://www.autoeq.app/

Well, personally I have the akg k701 and hd599, both are audiophile but the hd599 sound very good for games even in btf6, even on a console and without configuring anything. I hope it helps you