I ask sorry to anyone! Wasn't my intention be boring! Anyway, installed and tested RockBow : it works like a charm! Changed the value of treble/bass, and I've got the Sony quality (more or less), without any kind of EQ settings
That's what I needed!
Now I've only to understand some things about RockBox (like how to play all tracks in random mode on my pc, or how to add songs to playlist, but these infos should be avaiable here with an easy search)! It looks very nice, awesome project! Thanks again to everybody, and sorry again skip252 for waste your time!