[reptillian]

now forgive ignorance here, however I need this resolved. providing a DAP/PMP provides 37 mW of sound into a headphone, if I buy a portable amp which outputs 20 mW, will I now have a maximum of 57 mW per channel to use?

this is using a headphone out, as the D2(+) does not have a lineout.

 

[iriverdude]

Nope. You'll have 20mW

 

[Young Spade]

The amp will take in whatever is feeding into it and output at its maximum. That's like putting jet fuel in a car. Theoretically the fuel is "better" but the car will only go as fast as the motor will let it.

(Just a random example)