One might also suggest that the Sennheisers are terrible phone for portability, requiring as they do so much extra power and equalization to sound like a lower impedance phone. (I'm being facetious; the HD-25 is a fine headphone).
I love my iPod 5G and iPhone -- they both blow the lid off computer sources (Dell @ work, MBP @ home) in terms of noise floor and staging. The former has a decent DAC (a little noisy, a little shrill but better than many of my CD players and good sound flavor overal), good battery life, a ton of space and a good UI. The latter has an awesome DAC (a little sterile but utterly noiseless and high resolution), great battery life and an excellent UI, with add-ons like Pandora and SimplifyMedia that no music junkie can deny. And personally I just like the tools better, both hardware and software -- they allow a user to spend less time tweaking and managing, and more time enjoying.
My only gripe about iWhatever is the EQ. That software EQ clips like my mom with a coupon book and customization is non-existant. I'd love to be able to define a Grado-like equalization for my ATs and vice versa...but it's not worth giving up everything else.
I'm a little shocked Apple hasn't positioned the "classic" as more of an audiophile grade player. Custom EQ, extra low noise components, better caps, etc...they could probably squeeze an extra $50 out of us, easy. But then, nobody who heard the Apple "HiFi" would take such a player seriously.