I really don't think a portable can offer enough current for them, though I could be wrong. They say 250 ohms on the box, but you should pick an amp for them as though they're rated at 800 ohms. All the best amps for super high impedance headphones I know of are wall-socket-bound tube amps. the T70p... maybe, but it's still going to suck compared to a desktop amp, and be lacking in bass.
Most reviews of the T70/p complain that there is no bass, not bad bass or weak bass, no bass. So long as you're using an amp that isn't designed to shred impedance, they're right. If you're looking for a setup that is primarily or exclusively portable, the T70 will disappoint. They're hungry. Underfeed them and they will simply not respond below 500hz. Give them what they want, and they'll be the cans of your dreams.
Edited by IorekByrnison - 8/11/13 at 10:56pm