Audio Note SUTs - Are they worth the money ?

I am not sure that ALL Audio Note SUTs use silver-wired transformers.  For those, you pay even bigger big bucks.
A SUT or any other transformer, has no inherent impedance at all. Transformers merely reflect the impedances of whatever is attached to the primaries and secondaries, as the square of the turns ratio. Thus, since most MM phono stages will present a 47K ohm resistance on the secondary side of the SUT, for a SUT that gives a 1:10 voltage gain, the cartridge will "see" 470 ohms (47K divided by 100).

Like Raul, I feel that this business about "matching" the cartridge to the SUT is a bit over-stated.  You want to use a SUT that provides the voltage gain needed to drive your phono stage, and not more or less voltage gain than what is needed.  After that, it is a more complex subject to talk about improving the linearity of the response by using Zobel networks, etc, around the output of the SUT.  But that's not something built into any SUT I know about.  Like I wrote above, in this case, 1:10 would be more than "adequate". 1:5 might even work well for the ART9, but I don't know the gain of the AN phono stage.

With the ART9, you don't need much additional voltage gain from the SUT in order to drive an MM phono stage, maybe 10X would be overkill, in fact. So, if you're interested in doing this in a scientific and cost-effective manner, so far as that is possible, you might try some of the well regarded but less expensive SUTs before spending the big bucks on an Audio Note.  However, if cost is no object, there is no doubt that the AN SUTs are "very good".  You can't go wrong, as they say. I don't know why you would need reassurance from any of us on that score.

I personally think everything they make is "very good" and overpriced.