For some reasons I have never had the urge to using a SUT on my Koetsus. I have set up a few for my friends and heard them. The first thing is physical, as Mulveling mentioned, added pair of ICs, and, where do I even begin? Brands, brands, brands. Hum and shielding problems. I didn't want that anymore as in the past I was using an ET2 tonearm that did not provide its own cables and the cables I chose produced hum I had to move it here and there tame the hum level. Second is psychological. I want to have a direct (shorter is better) path, and I feel adding a SUT may be removing some 'purity' from the Koetsu cart. No hard science here, just a personal feeling. And finally, finding the right impedance. A friend's Phono stage didn't have separate MM/MC inputs so that sole input needs to be adjusted with the various loading values the phono preamp provides. Not very much a techie, I just listened to the setting with the least overload effect. And I had to go lower, as there were bass distortions in the high settings. Anyway, it's a good thing my Minimax phono stage has a pair of built in SUTs, with only 2 settings, high and low. I like the low better. Gain is 58db for MC.