I have information on the Supex SD 900, which in the notes says that it is very similar to the Supex SD 900 Super.
The reviewer ( J. Peter Moncrieff from International Audio Review ) states that the internal resistance of the cartridge is 7 ohms, stating that this is quite a bit higher than some other MC's. There is no mention of what resistance he used to load the cartridge with. With the factory recommended loading ( whatever that is ), it shows an ever rising response from the midrange up, a slight dip or "plateau" in the extreme upper mids / lower treble and then two bigger peaks way up top.
To compensate for the rise, IAR recommended "overcompensation" by using 4400 pF of loading. This drastically lowered the noise and actually produced a roll-off from the midrange up. He states that this helped compensate for what they thought was a "sizzly" top end while also trying to minimize the noticeable "plateau" that occurs in the middle of the rising response. Moncrieff tried other loading and felt this worked best.
Judging by the frequency response curves, i would probably try starting at about 800 pF total ( taking into account arm wiring, interconnects and phono stage adjustments ) and work your way up from there. The higher that you go on capacitance, the less apparent treble you will have. You should be able to find a balance that should blend with your personal tastes and system.
While this flies in the face of what Joe stated regarding capacitance and MC's, i'm simply relaying what was printed 20+ years ago. Sean