Well, if you don't have any case fans then your components will get hot and the fans on the CPU and GPU will rev up to deal with it. Anyway, I use a tower cooler so I can't really comment on the performance of the 955s stock cooler
. If it's your GPU, then it should only rev up when playing games or something. You can manually set the fan speed so that it starts off cooler and thus doesn't have to rev to those rather loud levels.