Thanks for the data Paul.
A voltage gain of 600 means a gain of 56 dB, so a fair amount of gain is required to get to a standard level.
Each system is different, but if you convert a low gain phono stage to a repro amp, you will need sufficient gain
in the rest of your system.
For example, the seduction gain is 36 dB.
For my system, where my "linestage" is unity gain, my amps have gain on the low side, and my speakers are not
very efficient, the seduction wouldn't work well.
If you have a linestage with typical gain (12-20 dB?), then the seduction would probably work fine.
If you are also using a unity-gain "linestage," that is, a resistive passive preamp or buffered passive preamp,
then a phono stage that has gain appropriate for a moving coil cartridge without an input transformer would be better.
They exist in all-tube form, but usually they have a FET input for low noise.