Then if that is the case, what would you paired with the 789 ? So in another words, not worth to own both ?Both systems are fully balanced. THX 789 is connected to D70 with Balanced cables, A90 is connected to D90 also with balanced cables. Both my HD800S and TH900 MK2 are using balanced cables. I would have to say, both amps are TOTALLY SILENT... Total blackness, cannot hear hiss or noise on both amps, with both XLR and RCA inputs. I know a couple of people complained about the A90 RCA input being noisy, not my experience at all. Back to my evaluation of both amps, they are both fantastic, I like them both. The 789 is the more airy sounding of the two, A90 has a touch of warmth to the sound, bass that hits a little harder and a more intimate sound stage... we are talking minuscule differences here. Again, I would admit I do not claim to have the best hearing in the world, but my conclusion is this... if you already have the 789, upgrading to the A90 is not worth it... unless you have a D90 and want to stack the A90 with it. Its more of a side grade IMHO, My 2 Cents.
At least the benefits of getting the A90 over the 789 is beauty. That Drop 789 is damn eye sore compare to the beautiful utilitarian Massdrop 789.