Will our MC for the festivities gain the stage?

Those of us who own preamps with phono stages are familiar with the phrase, “will handle MM cartridges and most MC cartridges”. The word “most” becomes critical when considering many of the low-output pickups available. My Kora Eclipse, for example, has separate MM and MC inputs and the MC stage is rated at .4mV/100ohm with a gain of 55dB. At what point is that 55dB gain insufficient to handle EFFICIENTLY a very low-output pickup? .5mV, .6mV? I know that it does depend upon actual output of the pickup and there are no hard and fast rules. I was given the following general guidelines some time ago which I post below. Does this seem like a good “rule of thumb” or is someone prepared to give it the finger, instead? Thanks.

0.2-0.5 mV needs 63dB gain
0.6-1.9 mV needs 50dB gain
2.0-5.0 mV needs 37dB gain