Alright, just received my replacement A90 from APOS. Big shout out to Apos once again for a super fast shipping.
Good news first. The new unit definitely emits less noise on RCA interconnect. On low gain with sensitive IEM, the noise was still there slightly, but no where as bad as before. I could probably ignore it if I had to on normal volume. On high gain, it is still very much apparent and non usable. No issues on high impedance HPs. On the other hand, XLR is very clean. No noticeable noise on all gain settings even with sensitive IEMs.
Man this thing is powerful. On balanced, with 300 ohms HP on medium gain, I'm comfortable on 10-11 o'clock on volume knob. SE has less power, but still kicks ass and sounds just as good.
Haven't tested the pre section yet. I'm afraid it'll fair poorly and just want to enjoy the music for now.
Sound wise, the A/D 90 stack may be touch bright on HPs with treble emphasis. But I think it pairs well with the mid focused cans like the HD650.
Overall, very pleased. Great value, especially considering its $500 asking price.
Gonna have to do some long-term testing, but for now I think i'll keep it in my stable.