Yeah, I have that one, an NEC 1970NX and BenQ... can't recall the exact model, B920L? That all support 15khz. The picture quality is listed in that order from worst to best for the ST, but the Dell has some dark swirls so it probablynormally has a better picture than mine. But I like the Dell the best because it also has Svideo and Composite.
The auto centering is weird, and I also have the issue where if you push the button to change inputs enough times to cycle back to the one you were already on, the colours get messed up. Not sure if that is normal....
Atari 8Bits: 800xl, 600xl, XEGS, 800, 130xe, 130xe (VBXE, U1MB, Stereo POKEY)
Atari STs: 1040STf (broken shifter), 1040STe, Mega STe, TT030, Falcon (CT60e, SuperVidel)