Wavpack supports lossless DSD compression. Anyway, support it or not, your choice. But all these upsampling stuff, measurable or not, I can't hear any improvement, absolutely. So these kinds of processing are not for me. Thanks.
Just curious what DAC are you using and how did you choose it? How are you using HQPlayer? You don't hear differences with digital room correction, 3D headphone processing or such either? To me, one of the many driving factors was to get digital room correction for DSD in proper way, without suffling the sample rate down and up.
To me, different digital filters sound different, also the ones built into the ESS Sabre, even if they have same stop-band attenuation. It is not the only thing, just one of the many many aspects. Also because at ADC or mastering side the PCM content we listen has been subject to digital decimation filters, leaving their own fingerprint to the signal and sound. With apodizing filters you can replace this.
When I worked in Navy, first training passive sonar operators to listen and use analyzers and later developing analyzers, I learned that ears are definitely good at certain tasks and analyzers at other things. But there's no huge overlap. And you can learn listening a lot...