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

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

Mihaitaa -- very helpful, thanks. FWIW, I think you're right. Or rather, that (my understanding of) Harley is way off.

Not only will a .25 mV cartridge work with 62 db of gain, it has worked optimally in my experience with 2 different cartridges and two different phono stages, neither of which were KAB phono preamps, for me over the past 5-6 years.

My previous cartridge was an Ortofon MC 20 Super with an output of .25 mV and it worked perfectly with 62 db of gain into a 100 ohm load using a modified DB Systems phono preamp (modified to give 62 db of gain) into a line input on an Audiolab 8000A.

I've also used (and am currently using) Denon 103R's which are rated at .25 mV into that phono stage as well as an Aqvox phono stage into the Audiolab mentioned above as well as a Jungson JA 88C integrated.

Both of the 103R's I've used in the past 4 years have come with individual spec sheets indicating slightly higher output than normal specification. One with about .29 mV and the other had .30 mV.

My Aqvox has variable gain on the balanced inputs between 60 and 75 db and I've run both of the above Denon 103R's at the lowest gain setting. In other words 60 db. Going higher is as simple as turning the gain pots on the front of the unit and I've done it.

Those cartridges work best in my system with 60 db of gain, not any more.

Too much gain (and not enough gain, for that matter) is not a good thing.

Yes 0.25mV will work into 62dB but noise comes into it at these levels. 0.25mV should ideally be used with 65dB as the lower you go in gain the more hiss you'll introduce. Imagine using 0.25mV into a 40dB (MM) then increase the gain to 65dB. As you increase the gain the signal-to-noise ratio changes 'balance' so you end up with more signal than noise.

I have a few turntables with a few phonostages. The Denon DL304 @ 0.18mV is a real problem for a lot of stages. Some of my audiophile friends 'think' that noise/hiss is par-of-the-course when using 0.18mV - 0.4mV with a ANY phonostage.
A friend uses his DL-304 with a Naim Prefix and all you hear between tracks is HISSSSSSSSS!

I chose to use the Whest stages years back because apart from the audio quality, the background hiss/noise was the lowest I had come across using a DL304. In fact with their smallest whestTWO which I have in my home/office I have plenty of gain and absolutely NO NOISE or HISSSSS. A sign of a great design.

I also use a Dynavector XX2 MK2 (0.25mV), new Ortofon A90 (0.27mV) and Shelter 901 (0.6mV I think. using various stages.

I've had no noise with the DB Systems stage (which is a very inexpensive phono preamp) and the Aqvox but reviews of both have noted that these are extremely "quiet" phono stages. Both are pretty much "CD quiet" both while the music is playing and between tracks. As you point out, it is a matter of the quality of the design.

Of course, it is always a question of YMMV and I think there is a legitimate caveat with respect to pairing tube phono stages and low output cartridges; in general, that can be a combination that leads to a fair bit of noise once you get into and past the high 50's with gain.

I guess I've just been fortunate to own quality phono stages at different price points but, as I said, IME the KAB calculator is just about dead on. Could be I've just been lucky.