I have an A8 for a few months now. It would take a lot more than the power supply to improve the A8.
Comparing between a Lumin U1 directly, the A8 loses in resolution, those micro details are missing and the soundstage collapses a little bit, the front to back is cramped some. There is a five fold price difference there.
The A8 shines though with NAA, even Redbook files upsampled to DSD128, listening on its own is very good. Mine is on 24/7 playing.
USB input is very much dependant on the signal chain, fickle input SQ wise, but functionality works very well. Haven't tried the TOS or the Line inputs, but nice to have these for flexibility.
Eversolo regularly updates functionality, features and bug fixes, they listen, will give them that.

