Can Cayin make a DAP that sounds better than AK380 Cu? I doubt.
Why? I suppose it depends on which company has the superior engineering and software know-how; either Zhuhai Spark, or iRiver. Let us not forget that "Astell & Kern" came from very humble beginnings as a decent but not terribly notable second tier DAP manufacturer pushing out such forgettables as the Clix and H10. Note that they produce NOTHING under the iRiver brand now. It's allll AK.
What they do better than anyone else in the space now? Marketing and design. They read the high-end audio playbook cover to cover and implemented perfectly. So now they have a premium product at a premium price with premium features and performance and a premium profit margin. Unlike high-end audio, they're the only ones in the DAP space executing this way, although others seem to be figuring it out.
What I notice? iRiver/A&K is driving design even moreso than performance. Look at the change in appearance from the first days of high-res DAPs (the HiFiMan HM801 had the space pretty much to itself for several years; the QLS QA350 was first but was really a DAC with WAV ability and rudimentary controls grafted on). The iBasso DX100 was about three years after, and the AK100 followed shortly thereafter. But AK upped the game on the tactile and visual experience and continue to do so, even if their initial efforts were poor on the performance front. The AK100 was not well regarded at the time.
If you compare the best of the best in DAPs, its much as with high-end audio, rate of return diminishes greatly as prices increase. Once you get beyond $800 in the current DAP market, its more about personal taste and bragging rights.
Having owned a home audio system totaling over $100,000 in value (B&W 802D, Edge NL-12.1 amp, Amazon Referenz turntable, Manley Steelhead preamp, ZYX univers cartridge, JL Audio Gotham sub, Studer A807 reel deck, Manley Tapehead preamps, dCS Scarletti SACD and DAC,etc) and having rolled components countless times (Avalon speakers, Jeff Rowland amps, VPI, Rega and Linn turnrtables, tonearms, cables, preamps, you name it), I quickly came to realize that once you cross a certain threshhold in price, the differences in performance become minute but the differences in cosmetics, features, and claimed benefits become much larger.
