Phono Preamp Gain

Hi all,

I am in the process of getting a new cartridge and I want to make sure the output voltage is a good fit for my system. First off here's what I'm working with:

VPI Prime
Schiit Mani (30dB, 42dB, 48dB, 59dB gain options)
Prima Luna Dialogue Premium Integrated (239mV input sensitivity using KT88 tubes) (S/N ratio 81)
JBL L100

My question is what do I use for Vout in this equation to calculate the correct gain to choose on the Schiit Mani phono preamp??


20log(Vout/Vin)


Using the input sensitivity of the integrated and the output voltage of the  Soundsmith Otello ES Moving Iron Cartridge I get 

20log(.239V/.00212V) = 41dB gain

Is this correct?
My main issue is I dont know if my assumption to use .239V is correct.

Cheers