If you get a low impedence 'phone it would be absolutely fine to plug straight into your computers soundcard, you may get some electrical noise and the sound quality won't be mindblowing, but it's deffinately passable.
DAC's are usually for us audiophiles with more money than sense, who laugh in the face of diminishing returns.
Some computers have too low output volume for full size headphones - some are just fine. A dac with hp out at $29 can do the trick - I wrote about my experience with the AKG 242 and computers and this cheap dac here
70ohm would be too much for an ipod i think, and is possibly stretching the limits of PC soundcard, i'd go lower like 25-50ohm.
I've just tried my hifimans directly on my PC's onboard sound and they work fine, not as loud as i'd like but deffinately ok.
If you're going amped, the Fostex T50RP is stupendous value, now selling at $75. They're extremely unfatiguing and has all the microdetail. Some might find them a little unexciting at first, but they are really wonderful. But if you're a treble- or bass head, you might find them slightly uninvolving, but then - you can't get it all at once. Doesn't throw detail up in your face by accentuating treble (as most high end phones seem to do), but all is there - just lean back. Well - I'll write on in a review or something.. It's a fabolous headphone :)) If you're willig to do some acoustical modding, it is supposed to be legendaric. I enjoy it really much in its stock form, though (for now).
$119 i'd think you'd be hard pressed to find them much cheaper.
Ardilla said it was $75 :| which is true if you go to B&H, but they sell out soooo fast T.T
Many thanks and gratitude :) Is pro-sound.com's stock already in? frontendaudio.com's hasn't arrived yet :|