At the risk of being controversial: sure, the Mad Dogs are not easy to drive. I've tried them on a variety of amplifiers including the Lyr, Asgard, Magni, Pico Power demo, a variety of amps I can't even remember the names of at a local meet recently, my Denon amp's headphone outs and a few old speaker amps (from the headphone out, not speaker taps). Regardless of whether my impression of them changed to the point where they had a completely different sound signature or significantly outperformed themselves with a different power source (they didn't), the fact is this: if you have to spend more on the amp to get the sound out of the headphones, why not just get the better headphones in the first place?
Figure this: I feel my HE-500s on the Magni is a much better listening experience than any I heard with the Mad Dogs. That rig is $800USD. I hear many saying the Lyr and Mad Dogs is a great combo (for example), I combo that would run approximately $750USD, and, to my ears, still not come very close to the first combo. So, even if the Mad Dogs DO come close, wouldn't it make sense to get easier to drive, more scalable headphones from the get go from a financial standpoint?
BTW- I'm not saying people should run out and buy HE-500s, I don't really care about the particulars, I'm simply pointing out that it seems like chasing the top quality from the Mad Dogs ultimately costs more than starting out with "better" headphones in the first place. Of course the 500s are open and if you're looking specifically for a closed can, this argument is moot, but I'm kinda surprise the quality/cost equation isn't considered more when the refrain "the mad dogs are not easy to drive" comes up over and over again.