Hi Hugo,
Martin's Hashimotos are very good indeed, and they certainly get the thumbs up from me. However, IME, the secret to success with an SUT is in achieving
synergy, sonically, with the partnering cartridge - and that means finding the ideal match.
Martin was lucky that he happened to hit upon such synergy, between his Shelter 5000 and the H7, but there's nothing to say that the same will apply with your Ortofon (Kontrapunkt B?) unless you've listened to your T/T, with that cartridge, in Martin's system? That principle also applies with the Music First unit, which you're considering. Who knows which cartridge will provide the idea balance with it, sonically? It's a bit of a lottery....
In my view, one of the easiest ways of achieving the desired synergy is to use a cartridge and SUT from the same manufacturer. That way, you get the benefits of them both being designed (and voiced) together from the ground up...
It's not simply about electrical matching, but more importantly the respective 'sonic signatures' of the cartridge, and the transformers used in the SUT, synergising together, in order to achieve the right sound balance. The last thing you want is an inherently toppy sounding SUT, paired with a similarly voiced cartridge (or the opposite), and no amount of fiddling with gain or loading values will cure such a fundamental imbalance.
With my extensive experimenting recently with various SUT, before settling on the Ortofon, I found this aspect of 'voicing' the SUT to the cartridge, out with of more prosaic considerations, such as gain and loading, absolutely crucial to achieving the most musical sounding results. Since you have an Ortofon cartridge, I would urge you to consider Ortofon's own top-of-the-range SUT, the ST-80SE, which I myself use:
Trust me, it sounds absolutely fabulous with my SPU, and also a Cadenza Bronze, I've heard it with, and I suspect that your own Ortofon cartridge would love it, too. Anyway, it's just another option for you to consider. If you fancy popping up for a listen, when you get back home, just let me know
Marco.