First, there is a nice writeup on calculating required gain on The Absolute Sound website, http://www.avguide.com/blog/taking-the-guesswork-out-phonostage-gain. If you plug your values into the formula (works nicely in Excel) you will see how much gain you need. One variable that hasn't come up in this thread is the voltage required by your amp to drive your speakers to an appropriate level, although the TAS write-up provides an "average value."
As for personal experience, I have an ARC SP-8 preamp, ARC 150.2 amp, and Maggie 1.6QR speakers. The ARC specs say that the gain using phono inputs is 60db, and with a .5mv Benz MC cartridge, I get very adequate levels with the gain control around 12noon, i.e. at least in my set-up, 60db of gain works perfectly with a .5mv "medium output" MC cartridge.
As for personal experience, I have an ARC SP-8 preamp, ARC 150.2 amp, and Maggie 1.6QR speakers. The ARC specs say that the gain using phono inputs is 60db, and with a .5mv Benz MC cartridge, I get very adequate levels with the gain control around 12noon, i.e. at least in my set-up, 60db of gain works perfectly with a .5mv "medium output" MC cartridge.