Hi,
I just wanted to put the word out that I've tried the Benq XL2410T that according to tech specs should be able to handle 15KHz.
I've been on a decade-long quest for a native 15KHz RGB LCD monitor. Back when that scan range was more common I got a used one that definitely had 15Khz in the specs, but not in the electronics. Since it was used, I couldn't return it, either.