it all really depends on the duration of listening to the music. Constantly listening to music day after day for long periods of time(say 8 hours a day...i kno who does that?) but 8 hours a day consistently you could permanently damage your ears at 60 db.
If you are talking immediate damage then i would say anything over 150 db would do immediate damage. My 97 pontiac Bonneville has 2 15" Kicker L7's powered by a Hifonics Brutus BX-2005D 2000 watt amp and i am puttin out 145 dB. I almost never crank it that loud tho. Only when showing off around school and work. I listen to my music anywhere from 60-100 dB daily (depending on how my day has gone)