What software has good sound quality?

If the streamer is doing DSP, then sure, it could sound better than a PC.  My PC sends the digital audio to a receiver with Dirac, so no need for a streamer in that case.

Frankly, all of them reads file and send data down the USB. Unclear to my why would they sound any different. Unless it is measurable that data down the chain comes different. But if it differs from the file, the software has a huge bug.

Guarandamteed streaming software can and may well in fact sound different. No two programs are exactly the same.

Add Roon to the list. Last time I compared a couple years back it was way better than Plex, even playing “vanilla” with no dsp. Add the right built in Roon dsp filters to season to personal taste.

Well executed DSP is a requirement for me now with any streaming. Roon does it very well.

DSP, sure. But otherwise the process is no different from copying file to an external USB hard drive. You can write copying code any way you want, but the result of the transfer is going to be an identical file.

I compared Roon and Audirvana a while back, but could not make out any difference. Tried hard, but nothing. I am not surprised as either app just sends 0/1s to DAC, just wanted to not-hear it for myself. I like Roon's interface a bit better, so use that.

From MacMini with SSD drive as dedicated Roon server via USB to Holoaudio May L2 DAC.