Using SP as an mp3/mp4 player

Hi!

I'm currently like one step closer to buying this device, I've been excited about it for the last month or so. And I wanted to ask:

• I heard there is a music player on it. Is it on stock OS, or some custom one? I want to use this boi to play games, but also as a dedicated mp3 player to replace Spotify.

• how is the sound quality with headphones? I'm no audiophile, I plan on using my wired KZ ZSN Pro monitors.

• can I watch some good ol' Shrek on it? And again, would that be on stock OS or something else?

So basically I want it to play all my ROMs up to PS1 and some PSP, some PortMaster games (Doom, Key visual novels), and on top of that have a second card full of music and maybe some silly videos. Can I do all of that on a single OS? Do I want too much or am I good?

Thank you for your answers, and excuse my possibly broken English.