I have heard a number of systems with Audio Note SUT, including my own, and they are very good. Given that you have an all Audio Note set up for electronics, it might be worth the price premium to stick with their transformers.
The thing is, there are plenty of quite good transformers on the market, and most of them will sound pretty good, if not quite the same as the Audio Notes. Almost any decent transformer matched to the particular cartridge and gain requirements of the system will sound nice. I sort of agree with Art Dudley of Stereophile who said that even when the step-up transformer is not a perfect match, it will usually sound good; he said that he has never found a step-up transformer he didn't like.
