Moving from the Esoteric P-05/ D-05 to the K-03

Correct...Esoteric/Onkyo told me the same thing; the X upgrade for the K03 and K01 allows for only the new board and DSD playback in native format. Buying a new K03X or K01X gets you many other improvements beyond the upgraded board. From the Esoteric Japan website;

"Four years after the release of the K-01—the world’s leading all-in-one digital player—the new K-01X debuts as a more compact version of Esoteric’s flagship Grandioso model. Utilizing the same type of highly rigid chassis construction as the Grandioso and a similar four-transformer power supply, it integrates the Grandioso P1’s high-precision VRDS-NEO “VMK-3.5-20S” turntable with two independent monaural DAC units derived from the Grandioso D1 design, each configured with a parallel array of 8 individual converters, which are summed to optimize linearity and minimize noise.
Electronic circuitry has also been further improved with the latest technologies, including a new AK4495S DAC IC, an advanced 35-bit D/A processing algorithm, an HCLD buffer amp, a DSD-compatible USB interface, and a large, low phase noise clock, all ensuring the K-01X achieves the absolute pinnacle of sound quality."

Much more detail on the US Website;

http://www.esoteric-usa.com/Products/audio-players/X-series.php

Syntax....I know, I faced the same confusion when the mention of the upgrade first came out followed shortly after by the announcement of the X-generation units (K03X, K01X, C02"X") in Japan. When I queried Esoteric/Onkyo and they did some digging they came back and apologized for the lack of clarity and then set the record straight....