Do the specifications state it can sync to 15.7KHz, or only as low as 31KHz?
The first number was tbe old TV 320 x 240 (320 x 263 PAL) non-interlace standard, the latter is VGA or 640 x 480 (576 PAL) if I recall correctly.
Dell made until recently monitors such as the ST2420L that sync'd as low as 15.7 KHz, had VGA, DVI, and HDMI inputs and a top resolution of 1920 x 1080