[Sordel]

Now that I'm moving away from using the onboard amplification on, say, an iPod, and am investing (or about to invest) in decent headphones, a headphone amplifier and probably a DAC, I've run into a source.

I'd like to get a portable transport, but while there's no problem getting a cheap DVD player with an optical/coaxial out to do the job, if I do that I'm paying for 1) a cheap headphone socket, 2) a cheap screen, 3) a DAC none of which I'm going to use, leaving me with about fifty cents' worth of bit reading. So, um, how come no manufacturer seems to produce an "audiophile" disc transport? After all, most receivers seem to accept digital inputs these days, so surely there would be some mileage in a source like the one that I'm imagining.

 

[Mr_Sukebe]

Strikes me that the key word in your query is "audiophile" portable transport.
Whilst I do believe that better transports do make a difference, to make a noticeable improvement on a cheapy DVD play they appear to require:
- Some serious physical engineering
- Higher quality power supplies
- Some good quality vibration damping
All of the above is expensive and heavy, neither of which really mixes in well with the typical Ipod user brigade.
Having said that, it's an interesting niche market, which I'm a little surprised that no one has really addressed.