First of all, thank you all SO MUCH! I appreciate all the feedback. Not a single person said "do a search" or made an unhelpful comment, especially to a new poster. Props to you all.
So it sounds like I've got two options, get an amp or get headphones that will perform near their peak potential directly from a portable device. The AD900s look like a good option to investigate. Any word on the Beyerdynamic T70ps? Headphone.com has them listed as coming soon.
But assuming I have my irrational heart set on the AKGs how much power do I need? Are they just on the edge of being efficient enough and pretty much any amp would work? I'm thinking something like an AirHead but ideally maybe a rechargeable option. Is that powerful enough?
They will take as much juice as you can throw at them with a portable amp, even including high-end DAC/Amp models like a Fostex HP-P1.
Fiio E11 is a good start and should power them reasonably. It will never be a substitute for a dedicated desktop amp but it's a good start.
Think of an amplifier as something more than something that will simply increase volume, a great amp will have full control
over the headphone drivers adding depth, bass, definition and general goodness all round.
Edited by Gwarmi - 9/9/11 at 12:33pm