Confused about gain: phono + pre, or just phono?

My point is that if you "underload" the preamp (load it to 325mV max instead of 500mV max, IF 500mV is its sensitivity) you will get less S/N ratio out of the preamp (less input signal with the same noise floor of the preamp = smaller S/N ratio).
You say that KAB tailors the calculation for their OWN preamps, with 325mV input sensitivity.
This makes perfect sense and only proves my theory that if your preamp has 500mV input sensitivity, thus you should use an outboard phone stage with 66dB gain to raise the output voltage of your cart.
Thus apply the mere definition of dB to get the needed gain to raise your cart output voltage to the sensitivity level of the preamp you'll be using. That's all I'm saying.
There are two variables to use in the formula, the output of the cartridge AND the input sensitivity of the targeted preamp that will receive the output of the outboard phono stage.

I might be wrong, but usually the preamps have 500mV input sensitivity, which will mean 66dB of gain required for the phono stage to bring 0.25mV to 500mV.
Going 62 dB instead will load the pre with 315mV at the input instead of 500mV.
Of course, the pre will pick up the task of amplifying to whatever the input level of the power amp is.
I dare to say that going with less than 66dB of gain at the phono stage level will work, only 66 dB will do better, signal to noise ratio wise.

My answer was only looking at the mere numbers and factoring in the main principle that, considering the noise floor of any amplification stage, loading it in its optimal zone will improve the S/N signal to noise ratio.
Thus there is no fundamental contradiction, so to speak, KAB targets a lower preamp input voltage, hence recommends less gain.
It could very well be that KAB reached the conclusion that the sweet spot of preamps input is less than 500mV? Don't know, I tackled this from the numbers angle only.
Many preamps indicate that they handle overloads very well, over the specified 500mV and harvest better S/N ratio in the process.

Usually 1V is the starting input sensitivity of power amps. The ones with loads of power will have higher numbers in here or else you won't get to turn your preamp's volume knob too much before being blasted out of your seat.
So I guess that it goes this way.
1. you have the cartridge and know from its technical specs what its output voltage is.
2. You have/intend to buy a preamp and you know from its technical specs what the line input sensitivity is. Usually 500mV (but I might be wrong here). This is not the sensitivity of the preamps' phono stage which you'll bypass if it already has one. You want to buy an outboard phono stage, right? Because either your preamp doesn't have one or the one it has doesn't satisfy you.
3. Now you use optimal_outboard_phono_stage_gain = 20*log(Vpreamp/Vcart) where Vpreamp is the line level input sensitivity of the preamp and Vcart is the output of the cartridge.
4. Of course it's not going to be the end of the world if you're a bit off, that's why I said "optimal_outboard_phono_stage_gain".
5. Take a look here: http://en.wikipedia.org/wiki/Line_level
Might see them MAX for consumer electronics at 0.447V