rkw
Headphoneus Supremus
He wants to play binaural beats (sound for meditation). All of those are overkill for binaural beats. Even the MDR-7506 is already beyond his needs.My suggestion is to buy the Xduoo X3 music player and install the Rockbox firmware, fairly low cost investment into a decent DAP (Digital Audio Player).
Then maybe(?) invest into headphones that are better then the Sony MDR-7506 studio monitors.
As I said before, binaural beats isn't demanding for audio reproduction. So many qualities that we often discuss on Head-Fi like dynamics, detail and resolution aren't even relevant for playing binaural beats. He should be fine just using his phone as mp3 player.