What about the output impedance of Line Out? Isn't it higher than the amp output?
The specs do not mention anything about the output impedance of the line out but with a higher signal to noise ratio and a high 1.5 volt RMS I don't think driving them is going to be an issue (iems that is), the headphone out though has the amp behind it's back so it'll be easier for it to do so. The best thing to do is to try it and see. I know that you'll get a higher sound amplitude on the HO. I plugged my momentum on the LO and controlled the volume and the amp was not necessary. I don't like using the DX50 amp because it does not seem to sound as good as my pico amp.