If you can minimize noise generated by Synology (LPS is recommended) and your router, you can get a very high quality playback of your local files and streaming from Qobuz/Tidal. I would recommend installing a Ethernet switch w/LPS as a central data point to route all the incoming data before getting to your choice of server or streamer. There are few options like English 8S.
For a high quality streaming, dedicated audio server or streamer is equally important so pick a device that is designed for audio. Check out Small Green Computer, they have a good selection of music players or servers (which will eliminate the need for a NAS).
As far as DAC, you got so many choices. I would steer clear of cheap junk being sold on Amazon and pick up a nice R2R DAC. Look into Denafrips, like Pontus II. If you prefer a tube DAC, look into MHDT DAC’s sold by Linear Tube Audio.
And lastly, pick decent LAN cables (yes they matter). Check out Supra CAT 8 LAN cables. They are being sold by eBay seller ‘zendada’.
Whatever you do, do not get caught up in the endless debate of what’s more important. Everything matters!