You can't hack an amplifier. driving the sound is a very small amplifier that will only produce a certain amount of power. Once it's maxed, it's maxed. The only way to make more power is to lower impedance.
find headphones with lower impedance (the greek symbol omega represents this). Most earbuds are between 3,000 and 30,000-ohms. The lower the impedance the louder they will be. Look at Kicker earbuds... they get very loud, and respond to about 35Hz, so bass is clear. Lucid highs, and warm mids. Very good for any music type. They are about $80.
Cialis Online Store, 59% discount
Beats by Dre makes a decent set, also...although they are quite expensive. They retail for about $180.
Beats by Dr. Dre Official Site ? High Performance Headphones from Monster
Both are very high quality, with woven fabric over the cords to make them tangle free. This means no twisting during your workout.