wow thanks for the fast reply! I found just what I needed there :) Maybe I should have looked around before posting xD But thank you very much my kind sir.

   I currently have the Sennheiser HD558's and a ASUS Xonar Essence XTS soundcard.  The software that comes with the soundcard allows me to change between Normal Gain (0dB for >64 ohms), High Gain (+12dB for 64~300 ohms), and Extra High Gain (+18dB for 300~600 ohms). I started out with it at...