Sorry. "Oberon", not "Overon". Like the character in Midsummer Night's Dream.
There are several reasons why it would not be a good idea to introduce a SUT in the OP’s system. First, most commercial SUTs offer about a 10X voltage gain. If you increase the voltage output of the OP’s cartridge by 10X, it would be ~25mV fed to the MM phono inputs. That would be more than enough to overload the circuit at least on anything approaching a transient. Second, the SoundSmith cartridge is an MI type, not an MC type for which SUTs are most suitable. MI cartridges, especially high output ones, have about 1000X higher inductance than a typical MC and thus do not do well with the net input impedance you would get if you interpose a SUT.