It's hard to say specifically, because there are so many factors that come into play. How large is your room? How sensitive are your speakers? How loud do you listen? How much gain do your amp and line stage have?
All of that being said, I would probably recommend at least 60 dB of gain for your phono stage, possibly more, depending on your ancillary equipment, room size, and listening preferences.
All of that being said, I would probably recommend at least 60 dB of gain for your phono stage, possibly more, depending on your ancillary equipment, room size, and listening preferences.