As of now, I am quite diggin' the Meze 99 Classics... they are, I think, 32 ohm impedence.. However, they all say how efficient they are.. even an iphone powers them well enough... So, if they are efficient, could a Crack or Crack2 power them? IOW, an "efficient" 32 ohm versus a tougher headphone like the AKG K712.. my other choice that is NOT good for the Crack?....