As long as you have a decent DAC there is no need to upgrade, you won't see the difference.
I didn't not compared myself the A1 with others SS amp, but generally the opinions of tube sound vs SS sound is this one :
SS amps can sound harsh but ensure the maximum fidelity.
Tube amps sound sweet, they are more musical, but this musicality is distortion, hence less fidelity to the recording.
So basically the A1 is Hybrid meaning it combines both ss and tube sound.
However it has a THD of 0,1% which could be better. And audio-gd's product THD is much lower.
Hence, it more like "do you want an euphonic sound ? or an analytic one, with high fidelity to the recording ?" although I think audio-gd has some sound tuning for more euphonic sound on their amps.
Thats about what i thought, thanks. Ill be getting my A1 a little after christmas.