Does the Mac driver on the Korg website not work or is it just not working with El Capitan?
I downloaded the Windows driver which is an all in one including Audiogate but when I did the setup I only loaded the Korg USB ASIO driver.
I have it set up with Foobar using the ASIO audio Compnent driver. I'm playing 16/44.1 right up to DSD 256
As for the sound of the DAC it's pretty damn good, Mr Scrarfussi can confirm.