Depending on your budget you may want to consider the Atma-Sphere preamps, which btw include (I believe optionally) what is by all accounts that I have seen an excellent built-in high gain phono stage. My understanding is that they would have no problem driving any amplifier in existence. They are also fully differential, which would be complementary to your Pass amp. They use 6SN7 and 12AT7 tubes, and also 12AU7's in one model.
Regards,
-- Al
Regards,
-- Al