has anyone auditioned the https://kitsunehifi.com/product/springdacgreen/?

I am looking at dacs - currently using an iDSD pro driving a schitt headphone amp-> Senn hd 659. Sources are rebook  flac and hi res flac (50-50) stored on NAS and played through foobar2k on win10pro (purpose built pc with h97 mobo, intel 4790s cpu, 16g ram, samsung ssd)

Has anyone a sense of the order of magnitude difference between these dacs and what is perceived to be the audible difference?