Phono stage and preamp overload

I’m in the process of setting up my first analog rig (i.e. trying to rely upon my digital gear for ease and building an analog system that’ll offer a different experience).  I’ve read as much as possible without asking some questions, so here goes…Basically, I’m trying to understand how to set the phono stage at an appropriate gain such that my line stage is not “overloaded”.  

Here is my relevant gear and numbers:

Line Stage - Bel Canto Pre3 (input voltage overload = 10 vrms; gain = 20 db)

Phono Stage - Pass Labs XP-17 (gain of 50/60/70 unbalanced or 56/66/76 balanced)

Cartridge - Dynavector 20x2 (0.5mv)

Amp - Pass Labs x250.8 (2.24 v at full gain; not sure if this is relevant or not)

I’ve read that dB gain = 20 log (Vout/Vin).  How do I calculate the appropriate phono gain so that I retain a reasonable amount of headroom and don’t overload my line stage?  My simple math leads me to setting a phono gain of 66, or 20xlg(1/0.0005), but I have no idea how that relates to the input voltage seen by the line stage nor do I understand whether or not Vout = 1 is the correct value).

It seems easy, but I remain perplexed…please help an analog newbie escape digital!