I'm new to Step Up Transformers

The Herron phono stage, now out of production but possibly available pre-owned, is another that achieves high gain with an FET based input stage followed by an all tube circuit. It was very highly regarded, one might say venerated, by some who frequent this site, before Herron closed down.

Isn't the Soundsmith Paua a moving iron cartridge? That's the mechanism used by Grado and some others. No SUT required.

I checked and the Paua is indeed a moving iron cartridge like all the others in the Soundsmith line. 

It is moving iron, but it has a .4 Mv output.  

The approach of using a hybrid transistor and tube to supply the needed gain for low output cartridges is to reduce the level of noise from using tubes exclusively.   

The use of a SUT also reduces noise as an issue and adds the sonic signature of a transformer.  If you want tube only amplification (no transistor stage or no SUT) you have far few alternatives.  I mentioned Aesthetix earlier as an all-tube design that sounds good (if a bit noisy); another good sounding example is made by Lector (quiet for an all-tube design).

Yes, it's a moving iron but a very low output, similar to a low output Moving Coil.