Pro version uses a different dac chip, should be better than the plus version. Check it.Thank you.
I think it is available only from aboard.
I will try to stick with what's available local, IQaudio DAC+ and IQaudio DAC Pro these two seems to be raspberry pi official and supported by volumio.
The pro one got built in amplifier and plus one don't. I guess I need the plus model, as I want pre outs.