Phono preamp or SUT for low output moving coil

There is a direct mathematical correlation, in fact. And the more voltage gain afforded by a SUT, the lower the impedance seen by the cartridge, which will be the input impedance of the phono stage (usually 47K ohms) divided by the square of the turns ratio (which is synonymous with voltage gain).

@lewm  is absolutely correct. My SUT allows both 15:1 and 10:1 turns ratios, and therefore allows a 47kΩ MM input to be seen as either 208Ω or 470Ω. It makes a difference!

Actually, you can change the load resistor in any MM stage to whatever value you prefer, if you can identify it and can solder.

I wouldn’t go so far as to say "any" since the input impedance may be determined by more than a single resistor, but it is certainly the most common way. Hopefully whoever is in there replacing  resistors knows enough to determine what is needed.

The caveat with going too far is that increasing the input impedance also increases the amount of noise that gets in, so there is a practical limit

I agree with most of what has been discussed, but would like to point out that there is no conflict between the use of an SUT and choosing a phono stage that has an accurate RIAA curve.  I guarantee that the the use of the two together can be serendipitous.

The question or the argument is how accurate is accurate enough?

Before this turns into another one of those senseless debate….the answer ultimately depends on what “accuracy” means to an individual and how it aligns with their listening priorities.