The output impedance from the jack on your receiver is most likely pretty high - 50 to 75 Ohms. The higher the impedance of whatever phones you select, the less frequency response aberrations and distortion there will be. Rule of thumb would suggest phones with a 600 Ohm Z as a minimum. The selection, however, would be quite limited. Maybe look at some starting around 250 Ohms and up. Then again, you might not care whether the frequency response is skewed or the possibility of distortion increases. Just audition a few pairs and find one you like.