I'm not aware of any comprehensive way of doing this; either for the Kronos specifically, or any keyboard. The best-placed person to do this would be the manufacturer, and I haven't found one with a comprehensive audition facility.
With that in mind, here's a few ideas:
The most exhaustive option is to find a nice person who might help you. Stack Exchange is not the venue, but there are keyboard forums which might be of help. For your example, there are forums dedicated to the Kronos. Perhaps if you ask nicely someone might oblige? This is more likely to work if you just want to hear one or two specific sounds. Fronting up with a list of 50 might stretch the friendship a little bit.
I've also had success in searching YouTube for comparison videos. However, these are not at all comprehensive, and you have to watch the whole video to see if it's got the patch you're interested in. Soundcloud has also been of use. Search terms like "[keyboard name] demo" are of use. In my experience, they sometimes list the patch names in the video, or in the description text.
For the record, I went through this exact procedure with the Kronos before I bought one about three years ago. I didn't find everything I wanted, but I did find enough to confirm what I needed to know.
The obvious non-answer is to find a music store with the keyboard in question, and play it yourself. But that's not practical for a lot of people; myself included. Or make a friend who owns that instrument. In fact, a friend did exactly that with mine last week.