According to Soundmsith you can use a step up transformer with their low ouput MI's. A 1:10 transformer will present 470ohms to the cartridge which is about as low as you can go.
A friend of mine has the Soundsmith Paua, which I really like - better than his Koetsu Rosewood & Lyra Helikon SL - but it needs to see about 800-900 ohms.
I would personally avoid using a step up transformer because of the lack of adjustment of impedance seen by the cartridge ( you can load transformers but that has issues ).
Also I feel any gains from going to the low output can easily be lost with the addition of a step up transformer and cables.
The 2 options are if you run a low output Sounsmith MI get their matching phono - its quite reasonable and stands up to both a Lamm & Linn Uphorik with the SS MI - I've tried them.
OR
Look at their medium and high output options.