I don't think it is enough gain. I have a Shelter 501 with .4mv and my MFA Magus preamp has 66db of gain, and if I plug straight in to the preamp, without using my Cotter Step-up transformer, then I have to turn up my volume to full to get even marginal listening levels.
You might have slightly different results, but I think that is is too marginal to risk that. Too high a probablility that your volume level will be too low.
I think that if you like the low-output cartridges, like I do, you should get a 20db step-up transformer and use it in line with your phono cable. That's what I do. And you don't lose any signal with a decent transformer. You are dealing with miniscule signal levels which are not going to saturate any transformer. And the transformer also provides a better impedance coupling than going straight in. Kondo Audio Note-Japan, states that they recommend using a low gain phono section and using a step-up transformer for this reason. I use a Cotter, and I am very satisfied, and my system is so ultra-revealing that I can hear if a bug farted in the recording studio. On some recordings, I can hear the master tape deck running.
So, you are not going to lose anything by doing this, and you can gain cartridge choice flexibility, and try out some of those low output MC carts you've been hearing about. You don't have to change preamps, or dump any of your other equipment. If you do change preamps, you can keep the step-up transformer, because it is a separate box.
Total flexibility, and great sound, and improved selection range of cartridges. Sounds like a good idea to me.
Also, the 309 will handle all the cartridges you mentioned.