HOW MUCH GAIN ?????

There is no short answer to your question. It all depends -- mostly on the output of the cartridge. Normally, you need about 45-65dB for MC cartridges output ranging from 0.25-0.5mV. My 0.2mV Koetsu requires at least 65dB thus I had to sell the Audio Research PH3 (48dB) and get the Reference Phono which uses a step up transformer. Line section requires no gain but most active pre-amp has about 6-20dB gain built in. Some preamps have input attentuators to for fine adjustment between different sources.

I would recomment 60dB and more.
( I use a system with 0.2 output without any problems )
There are a few factors when choosing a phono stage depending how serious you are using your system.
An excellent phono stage is the secret for this kind of reproduction and there are some more things which are important too:
-Gain alone is not the secret
There are some units out there with high gain sounding dead and lifeless
- Important is:
the more you can adjust the better !
Gain, Impedances,Resistance
the newer cartridges with higher output ( Benz ...) were not made because they sound better ( nonsense ) they were made because most phono stages are inferior with low output MC's and the customer is more willing to change a cartridge than the phono stage.
To find interesting Phono Stages is no big secret, there are only a few manufacturers who are intelligent enough to build an outstanding one
( Vendetta, Klyne, Rowland, Pass ...).
But this is another story.

Thomasheisig, I agree with your evaluation, and would like to add the Aesthetix IO to the list. Are you in Europe?