equaliser put the audio signal into more components, more signal path thus exposing the audio signal to many alterations and reducing its purity.
at home, i was using mainly mini compo to listen to my music before i move to separates (source - amp - speakers). After the move, obviously more clarity in the music. Yes i spent more $ than the old mini compo but even with the newer version of mini compo, the sound from mini is compressed.
at office, i bought another mini a year ago. If i play the music with "jazz", or "rock" the sound is compressed. The "flat" mode yields the best result.
in my opinion, a good CD is engineered by good music engineer and does not need to be tweaked by the equaliser. Unless you crave for the overwhelming bass or overdosed treble (thus changing the overall tonal balance), i dont think you need an equaliser.
regards,