I agree with reubent. I have a Synology NAS on my wi-fi that is feeding my Oppo 105. You can attach your Qnap to your Oppo either wirelessly (with the supplied wireless dongle) or wired via an ethernet cable if both units are relatively close to each other. My Synology was connected wirelessly in my initial setup but currently is connected via an ethernet cable since it now sits right next to my Oppo. Both methods are indistinguishable connectivity and sound wise in my system (using a Comcast hi-speed wi-fi network). I use a laptop running JRiver media center software connected to the wi-fi and both components, too. You have this option if you want the benefits of automated megadata and the other capabilities of JRiver but it’s not required.
Both the wireless and wired connection methods stream the NAS music files through the very good internal dac on the 105 (with expensive Saber 9018 dac chips used on many hi-end standalone dacs) with the analog output sent to both of the 105’s main stereo outputs: rca and xlr. Both methods are also equal to or superior to using USB connections. As long as you connect to your 105 either via the wireless or wired ethernet inputs from your Qnap, the digital signal will be converted to analog by your Oppo 105’s DAC. You don’t need to change a thing.
Enjoy,
Tim