As an owner of a K-01X, I agree with Zephyr that you need to be patient with the long break-in schedule for this unit. Exercise each upsampling and filter option for hundreds of hours before jumping to conclusions about which settings work best. FWIW, after long hours with each option I have settled on 8x upsampling and SLDY2 filter. I’m looking forward to eventually comparing the external HD Player software filters and 2x DSD upsampling to the on-board options. With that in mind, it's useful that Esoteric thought to include unfiltered PCM and unfiltered DSD settings.
Once you become familiarized with the K-01X, a 10Mhz Rubidium clock with a 75 ohm output like the Stanford Research Systems PERF-10 is a meaningful upgrade, with greater impact than any of the CDP’s upsampling and filtering options.