Yes, PowerDVD 15 supports 5.1 surround sound playback.
Yes, PowerDVD 15 supports 5.1 surround sound playback.
The DAC from Amazon could affect audio quality if installed correctly. Since you're using it only with your Nvidia Shield TV, it's likely minimal impact.
I use PowerDVD and it plays Blu-ray in TrueHD and DTSHD formats when the disc allows it.