i dno man do you really need another device to play mp3s... it seems really trivial.
If Sony actually let people use MP3s they can listen to while gaming. Custom Soundtracks from the machine. That would be great especially for RPG lovers.
Keep a phone or tablet next to you (something most people already do). It's more convenient to switch tracks and control volumes independently. MP3s on consoles was novel in 2001.