And actually the AT-ML180 and many other best ATs perform best at lower values 20-30 kOhm and very low capacitance at 100 pF IME. My ILLUSION preamp works at 20-30 kOhm range at best for all my MMs.
@harold-not-the-barrel Maybe you don’t need a cartridge with such high frequency extention if you think, in your system, you have to load MM carts at 20-30k Ohm to roll-off high frequency (this is what you actually do when you loading it at 20-30k Ohm). At the same time you said ART9 gives you more refined high frequency extention than AT-ML180 (no wonder because you rolled-off high frequency with 30k Ohm loading for MM). Or maybe it's time to change the ATN180 stylus :) ?
In my system with high efficiency full range drivers i prefer to unload MM cartridges using 100k Ohm, especially if the cartridge sound is too dark. Or just 47k Ohm, but not lower.
System dependent, i believe.
P.S. I’m curious what is your speakers ?