MP3 sound quality

Which headphones are you using? The Clip players work best with earphones or headphones that are 16-32 ohms(especially 16 ohms) and are very efficient. Using headphones over around 60 ohms with my Clip players and without a supplemental amp I do notice a decrease in sound quality. If you have higher impedance headphones(over 60 ohms), you might want to try using a Fiio E6 amp(around $25) between your player and headphones. This even  lets me use my 150 ohm and 300 ohm headphones with my Clip+.