More than enough power to drive with a big BUT. The e11 is not the the best pair with the k701. It cannot give out the full range dynamics of the k. Used with the proper amp, i dont understand why a lot complain of the k having not so good bass body. This headphone was awesome!
I dont know if this is a typo or the whole post was a typo but I agree that this headphone "is" awesome... until you hear the older versions.. thus, turning "is" into "was"

i really suggest to use a desktop amp, whether it is solid state, or tube-based amps when using the k701. i like the sound of tubes with the k701
E9 as a starting amp, and maybe the O2 as an mini-upgrade as it will sound great with the k701 according to some bros here. these two amps are great if you really dont want to spend alot (for now) on better amps.
as for portable amps, they say the XO2 sounds great with this one since it really gives bass (if you really need it) and the XO2 gives alot of power as well.