Hi Ed,
I doubt that anyone can say definitively whether or not you have any sort of compatibility issue as far as the Allaert and the SUT in your phono stage. The following is a "guide" to SUT matching:
http://www.vinylengine.com/step-ups-and-mc-cartridges.shtml
I have no idea if this guide is helpful or not. Built-in stepup transformers in a phono stage are kind of a hit or miss deal, because the ideal transformer characteristics depends on the amount of gain you need and on the source impedance of the cartridge.
As far as the proper loading into an active phonostage, the Allaert distributor insists on a very specific loading (at least that is the case with the cartridge my friend owns). This suggests that the cartridge is very sensitive to proper loading.
My own experience with other cartridges is that proper loading is very system specific, so at best, a range can be recommended. To some extent, one juggles a variety of adjustments interactively, rather than as discrete adjustments. For example, if you have tonal issues, such as a cartridge sounds too bright or lean (lacking in midbass), the best setup might involve a combination of increasing the loading (going with a LOWER number for the loading resistor) as well as lowering VTA a little.
I know this advice goes against the school of adjustment that says that there is a very specific loading for each cartridge, based on its electrical characteristics. However, in my experience each cartridge reacts differently to loading, depending on the phonostage.
