What software has good sound quality?

I like Kodi the best.  But I am upmixing to 7.1, and to me it has the best sounding upmixer.  It has a lot of other problems, but Kodi gets that much right.

Upmixer aside, quality is not much of an issue in front of the DAC.  When you are using USB or HDMI, the digital audio will be bit perfect.

I do run my audio through a program called FXSound that I think makes it sound better.  But it is modifying the digital audio, not making it more accurate, it's already bit perfect after all.

While it has been a while since I compared software, I tried Foobar, iTunes, JRiver and a couple more. The difference was virtually inconsequential in comparison to getting off of the PC and MacBook and using a dedicated streamer. 

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. 

Thank you and do understand that in theory all should sound identical - but the do not in my system. Jriver sounds warmer, foobar thinner and more detailed - I know that should not be the case, but it is.