Best gain setting on phono pre- low/medium/high?

I have a phone preamp that permits three gain setting, 56dB, 66dB and 76dB. All three are usable, just need to adjust the volume on my preamp differently. What's the best thing to do- use lowest phono gain and more preamp gain, most phono gain and less preamp gain, or stick to the middle settings? 

I know this sounds like the 3 bears. 

I recall reading sometime back that keeping the volume control higher has advantages 

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Nothing to do with the three bears.  There is a an exact reason why your phono stage has three gains settings. 

What's your cartridge and specifically is it a MM or a MC?  Also, what phono stage do you have because a min of 56db is pretty high for a MM. 

Running an MC cartridge (Linn Arkiv B) -  these are the available gain settings for MC cartridges that my phono pre offers (pass xp15)

I should have specified that 
Thanks.  Your cartridge has an output of 0.4 mV so I would use the 56 or 66 db gain settings and see what sounds best.  Even though your cartridge is a low output MC, it isn't that low to consider the 76db setting.
I've never used 76db- that was too much
The lower the gain setting on the phono, the higher will it's overload figure be, a very good thing. Balance that against the noise penalty of a lower gain setting. With lower gain from the phono, the higher the line stage volume control can then be, also a good thing. Volume pots track left and right balance better at higher settings than at lower.
Bdp24, that makes lots of sense. I'm now running the phono on the lowest gain for MC and I've got plenty of room on my volume control on the preamp to reach satisfying levels. This seems to be the way to go.
All good advice. Both my phono preamp and line preamps have several gain settings and I found that the most critical gain setting is at the phono stage level. You want to use the lowest gain setting that allows a good rotation on your line preamp. From my experience, too much gain for a given cartridge's output results in a harsh, shrill, and overall unpleasant sound. Using the KAB calculator, which I find to be quite accurate, the optimal gain for your cartridge is 58 dB so it makes sense that you'd find the 56dB level to work well.
Very cool. I never saw the KAB cacalculator before, though I've been to the site. Learn something new every day ! 
I used to run my phono gain at 60dB......with the KAB calculator I set it at 56dB and find the sound much more appealing.