Quote:
Originally Posted by
MarketMarksman 
Bought the fiio combo, seemed like the most options for fair price
Based on the measured performance and a little theory (sorry haven't tried it myself), E7 by itself should be
better than E7 + E9 for the AH-D2000. Performance of the E9 amp is respectable but not really any better than the E7. It just has more output power, which you won't be needing for driving the AH-D2000 into very loud volumes.
E9 has the disadvantage (though arguable) of around 10 ohms output impedance, significantly higher than the E7. This reduces the damping factor and is supposed to muddy the bass. (AH-D2000 have pretty flat impedance across the frequency range though.) Also, the E9's analog volume control is more liable to cause channel balance problems than the E7 digital volume control, at lower volume settings. Channel balance on the E9 is not really problematic though.