My MC46 has a headphone jack on it, but I haven't really used it other than just to try it for a moment, as headphones have never been a priority. I really doubt I would use headphones outside of straight from the iPod, not that I wouldn't enjoy a better setup, just being realistic in the way I live. So, if I ever do go up in class over my PX100's, whatever I'd choose would need to work with the iPod, hence my question(s). I also use them ('phones/iPod) at night if/when I have trouble sleeping, so smaller equals better, but I don't like buds...maybe it is just the stock apple buds turned me off to them.
It is a "bummer" that the Cardas upgrade is so much better on these 'phones, as once we ('philes) know this, it is a must to do so!
My PX100's, while not on par with your 701's, also took a long time to break-in, they were a bit too dark for me until the finally "came to".