Beyond the basic troubleshooting, there are plenty of threads here on how to get best possible sound from BSN. If you’re new to streaming, there is a bit of learning curve (probably not as deep as your analog) so you need to be patient and allow BSN to settle in your system. When using a external DAC, make sure you’re using a good digital SPDIF or USB cable. You mentioned hearing a slight metallic sheen in your music with BSN, here are couple of things you can do to restore naturalness to the music,
1) Upgrade Ethernet cable to Supra CAT 8 (buy from eBay seller zendada)
2) Upgrade PC cable to Shunyata V14 - C7 or similar
3) Try a inline LAN filter like Acoustic Revive RLI-1GB-TripleC (buy from eBay)
All of the above tweaks + external DAC should help you get most out of BSN in its stock form. There is power supply upgrade as well for additional $258 but I wouldn’t go that far yet.