I recently purchased the 1.33ghz 12" powerbook. When I plug my nice Sony headphones into the headphone jack, i notice that anything under 100hz is really distorted no matter how loud or soft I turn the volume. Is there something wrong with my sound card or are these sound cards just crap? Even when I turn down the EQ on low frequencies in Itunes, it still sounds either distored or simply not present. Any advice would be greatly appreciated. I think I'm heading to the Apple store tommorrow anyway. Thanks!