[onocentaur]

Does such a device exist?

It would be cool if I could get something that would plug into my portable hard drive which could read the music files, then output to a (separate) DAC to amp then phones:

The result would be a semi-portable set-up with high storage capacity and great sound

 

[artears]

A laptop?

You can use its hd in addition to your external hard drive as well...

Semi-portable with a laptop backpack...

 

[Mr Do]

Something like a Lenovo thinkpad x series would be your best choice for an ultra portable laptop. (3.5 lbs)

Enjoy.
DO!

 

[onocentaur]

Now I hadn't thought of that!

That's not a bad idea.