Calculation verification please

Atmasphere!  Thanks for the clarification!

Atma, Skos wrote: "I’ve been experimenting into a MC section and the manufacturer says to load between 100 - 800 ohms. I’ve tried 250, 324, 368, 404, 500 & 600 ohms and found I like best the 368 ohm loading. So now want to try using my SUT."

IOW, he heard differences in SQ among those listed load resistances BEFORE he decided to implement a SUT. So, using a step-up had nothing to do with his observation.  So many hear differences using load resistances that differ by only a few tens of ohms that I am convinced the observations are valid.  I just don't hear it, or better to say I do hear subtle differences between widely different loads (e.g., 100 ohms vs 47K ohms, with LOMCs that can drive 100 ohms) but none worth a damn. In those cases I slightly prefer 47K ohms. I do think my system is low enough in distortion that I should hear it if my brain says it's there.  That suggests my ears and brain are tuned differently or are superannuated or both.

My wife is a brunette and I don't have the gut that guy has, but otherwise there is some relevance.

So yeah:

• For a typical fixed 47Kohm MM input, a 40x SUT gives your cart a 29 ohm load. You CAN’T raise that 29 by paralleling anything. If you try to add resistance in series, you will lose almost all of your actual signal before it hits the MM input (voltage divider). As mentioned earlier, you have to either modify the phono stage to get higher than 47K input (600K = 375 * 40 * 40, as mentioned ealier) or switch to an MM stage that has non-standard loading options above 47K.
• Rogue Ares has an MM option for 100K and 1 MEG ohm loading in MM mode. Phono stages with this kind of option are few and far between. 1 MEG would give you 625 ohms off a 40x SUT (1 million / 40 / 40). 100K is 62.5 ohms. Still, you target 375 eludes you. 
• A 1.4 ohm cart will be FINE into 29 ohms. Like lewm, I don’t see much value in going higher. I don’t hear much difference in small gradiations of load, at least until you’ve gone way too far (low ohms) for the coils at hand.
• Your 1.4 ohms screams "My Sonic Labs". If so, these carts also have high outputs - like 0.5mV. A 40x on this (20mV) is going to push you way towards the overload margins of most phono stages, which will likely have a very negative sonic impact - much more so than your loading concerns.