In my opinion, the 701 is not that difficult to drive; it seems to me that a lot of people (not all--don't get me wrong) try to change something about its sound signature through amping, so they go through several amplifiers to see if any one of them can change the headphones' sound to their liking.
Thing is, amping a headphone doesn't change a headphone's character much, if at all. If anything, a good amp will only provide slight refinements to the sound--barely noticeable to most people. For example, Uncle Erik has stated that he has tried the 701 connected to many different high-end amplifiers, but he still dislikes it, noting that they sound off no matter what.
One day, as an experiment, I connected my 702 to my laptop and turned the volume up to 100%, which was way too loud for normal listening. I then played some bass-heavy hip hop and electronic tunes and was pleasantly surprised at how deep the 702 could go and I heard absolutely no distortion or clipping... As far as I'm concerned, my laptop handled the 702 admirably, and I lived happily with that setup for over a year and a half. I'm not claiming that dedicated amplifiers are useless, but I am saying that for most headphones, their importance is overstated.
Point is, try the 701 without a dedicated amp. If you don't like it, chances are amping it will not change that. Just remember, when it comes to high end headphones, the quality of sound one headphone puts out is only determined by your ears and your preferences.
Anyway, if you do decide to purchase an amp, the M-Stage, M3, Heed CanAmp, and Dynalo have all been highly recommended for use with the 701/2.