FLAC streaming quality vs. Amazon HD on Bluesound Node

Have a first generation Node connected to Vanatoo Transparent One Encore powered speakers via Audioquest Cinnamon toslink optical cable (Node 1 doesn't have coax out). My FLAC collection is stored on a Synology NAS. Most of my FLAC files are 16-bit rips from CDs created using Exact Audio Copy, but I also have quite a few 24-bit FLACs from Qobuz and HDtracks. All local FLACs are tagged with Replay Gain (track gain) using foobar2000 software, and I have the track gain setting enabled in the Node's BlueOs software. When I started streaming music from Amazon HD via the Node's BlueOs software, I immediately perceived a general improvement in sound quality. This seemed odd, so I compared many, many local FLAC files to the same songs streaming from Amazon (ensuring that the bit rate was the same in each case). In the majority of those song-to-song comparisons, Amazon sounded a little fuller and more detailed. I'm stumped as to why this would be the case. I have a lot of time invested in my local digital library and I'm not ready to bail on it just yet. Plus, it kinda bugs me that a good percentage of my files perhaps don't sound as good as they could. Has anyone experienced the same thing? Any suggestions would sure be welcome. Thanks.        
 Let me preface by saying I am not a streaming savant, but I would try playing your music without replay gain and remove any track gain from Bluesound first.
You might be adding a filter by using such add-ons.