I like what Pani said. My Ortofon MC2000 is relatively new to me and my system. I got that thrill of discovery when I first auditioned it (without a SUT into my modified super hi-gain Atma-sphere MP1 loaded at 47K). And I think I reported my results here, to credit Raul with his citation of the MC2000 as one of the greats. Now here it is at least a year later. I have spent a lot of time in the interim listening to my other (Beveridge) system, which runs with either an Acutex 320STRIII or a Grace Ruby. However, whenever I go back to the MC2000, I feel the same giddy thrill. Proof of its enduring excellence (to my ears and brain).
There is a paradox with very LOMC cartridges. If one must use a SUT, then one cannot effectively experiment with "infinite" (very high resistance) phono loads, because of the effect of the turns ratio of the SUT upon the impedance seen by the cartridge. Thus it may be the case that one cannot fully experience the best performance of the cartridge, if in fact infinite loading is the ultimate. I really don't know and don't claim that this is always true. It seems to be true for the MC2000, however.
Can anyone explain the differences among AT7, AT9, and AT50? Are they available in mono versions?