Without AMP HP100 would not give you all that bass: detailed and well structured down to very low frequency. On the previous page I talked about the sound from iPhone5.
It seems that impedance curve do have a peak on the low end. The mid bass would present, but sub bas would change to very soft and weak. In other words, directly from iDevices you'll get a fall in frequency respond below ~100Hz.
But with Denon D600, bass is well present with iPhone5. In fact without amp D600 is more bass sounding phones, than with it.
I didn't get a chance to try them with an amp the first time I had them so I've ordered them again to try them with the C5D.