On the juice for the HD600, quantity matters less than quality unless you have a severe deficit we're talking about something that lacks both altogether (sounds like crap on a 5mW+5mW rms iPod, even a 31mW+31mW max Cowon, but it's good with the HM602 and I heard it's great with the S:Flo2). I've tried mine with all sorts of amps and they all sound different, but barring most portable players, they did well. My "reference" rig now is just the HD600 straight off my 20-year old Marantz CD60's headphone out, and the difference with a Little Dot MkII between them was far from night and day. I have the foam driver covers off though so that might have increased the sensitivity a bit (if it was measured from behind the veil and then without it.)
So there is a chance that if I put it on high gain, I might actually get enough juice and be pleased with the results? Obviously I won't know until I try it, however.