Dear @lohanimal : At the end seems to me that you don't need any SUT.
Look Through 3 TTs I have mounted 10 tonearms/cartridges and I always use it only one phonolinepreamp and at each time that I want to listening another diferent of the mounted LOMC cartridges I only disconnet the tonearm cable and connect the cable of the other cartridge. This task takes me 1 minute to do it.
Now, I use ( time to time ) SUT's because I owned from several years now but normally I listen the LOMC cartridges with out SUT and directly in my active high gain phonolinepreamp that comes with two totally separated duaL MONO FULLY BALANCED MM and MC stages.
Repeat, I don't need a SUT and seems to me that you neither.
R.