Greg, there are two cable optimizations RJ45/HDMI that really benefit the HD621, you can see them in my sig.

In my system I constantly try pushing both my Sooloos playback aswell as multichannel playback. I've for example all linear PSU's on MC200(SSD) and Gbit router. Mounted Furutech AC-1501 IEC inlet filtered on my Dune HD Base3D (MCH FLAC).

All these things add up and MCH and 2CH can certainly be identical in quality provided the same care and quality is used throughout the system.

DSP8000SE, DSP7200SEHC, DSP5200SE sides, DSP7200SE rears, 861v8, 210, Sim2 Ultranero 4, Stewart Cinecurve 2.35:1, XEIT CM-5E Anamorphic lens, Dune HD Duo Cinema 8K and Wireworld Platinum 48G HDMI -> UHD722 -> Shunyata Omega Ethernet. Shunyata/Furutech power-cables/filters. SR Master Fuse@861v8. Uptone Etherregen with 10MHz OCXO clock.