Thank you i understand better now , it just was not making sense to me :)

So please excuse me for being a bit slow but can you please help me understand why the Xonar wont drive the DT880's (250 ohms) , the Xonar essence STX has three headphone impedance settings from , +0dB ( 0-64 ohms) , +12dB (64-300 ohms) to +18dB (300-600 ohms ) and the DT880's have 250 ohms ?

So you would recomend and Xonar > amp > DT880's over the AD1000's with the Xonar ?  

The DT880's are only 250ohms the AD1000's are only 40 ohms ?  

Hi, I've just bought some AD1000's and an  Asus Xonar Essence STX . The problem being i wanted the DT880's (250ohms) but was told that the Xonar would not be able to drive them . I've been searching forum's and have found conflicting reports ? So can someone please help me out with a more...