Yes, you are double amping by using the internal amp. Which is another reason why I would never use said internal amp. Anything with a headphone jack has an amp in it. Not necessarily a good amp, mind you, but in order to make sound there must be some form of signal amplification going on inside the device.
Man, I had high hopes for this one. I mean, it's Blue's first headphone, so I'm not surprised that they made a lot of poor design decisions, but it's still disappointing.
Guess I can still buy one once the price goes down and mod the tar out of it (if it's actually as bad as everyone says that is).