How to go portable??

I wouldn't go for tube headphone amp cuz it won't be portable anymore. You should never bend it and you can't cary it in your bag. You should look-up Headroom ear-amps. Consider AKG240D.

What's the purpose of portable? If you are going to be in noisy environments I can tell you the etyomatic headphones are great. But if you don't need that level of portability or isolation I like my Stax system (it's SS--but I've been thinking about tubes for it a while now)

Thanks for the responses, I am traveling to Belfast and need a small transportable system. Once I get there I will be parking it but I need great sound in a very small package.

Thanks.

I like panasonic 470 cd player - they have MASH technology that tames the steely digital quality.