My dream portable,which just may happen is...
OQO Pocket PC - http://www.oqo.com/products/
Pico/Predator or whatever is the best amp/dac at the time
Grado RS1 for non-noisey environments
Sennheiser HD650 also for non-noisey environments
IEMs for noisey environments
Real good cables.....altho at the short lengths,it doesnt make a huge difference,but if im going to spend that kinda money,ill buy good ones.
With the OQO PC, you have all the music listening comforts of home. It has a built-in 120 GB HD, but you can always plug in whatever external HD you want in the USB port,so its unlimited. You can also bring an extra battery or external battery booster.
As far as fitting in a cargo pants pocket, it may,but you better tighten your belt well,or wear suspenders
I cant see anything beating this setup for a portable. Its practically a portable/home set up.
And its wireless also and you can download songs on the fly and look at head-fi while listening, cuz its a real PC mini laptop. You can have a real EQ,or use Winamp ,ITunes,Zune Player,Foobar,or whatever you want to play your music. Listen to internet radio,watch a movie,etc.
Heck you can be gaming portable also,or chat,etc.
One day ill have it (hopes).