The choice of opamp for the headphone is very much dependent on which headphone you are using. The choice of opamp for the line out is dependent on your speakers. I have been listening to Bela Fleck and the Flecktones through the HD650 and the NS1000M. With that combination, I like the LM4562HA/LM4562NA. But when I substitute the HD650 for the K701, then my choice is LM4562NA/THS4032CD.
So the opamp pairing is not so straight forward.

