With a Sony MP3 player, you're assured of a high sound quality while listening to music. A number of Sony MP3 players support Hi-Res audio. This plays Hi-res audio files, so you hear more detail in your favorite music. With an MP3 player, always look at the memory and whether it's expandable. When the memory isn't expandable, you can only download a certain number of songs. The more GB the memory has, the more numbers you store.