Compatibility between preamp and amps

With digital sources that output at higher voltages than most analog ones the 11 dB gain in the pre may be beneficial. You have 41dB of gain total which should  be fine. One thing I question is the amps sensitivity. At 0.85 volts, it is very sensitive if that is all it takes to drive the amp to full power. The sensitivity of the speakers also come into play. 

Yea, a 0.85V sensitivity 30dB amplifier is a candidate for a passive pre. Not to say that I prefer that route. I am currently using a active tube line stage preamp that has variable gain output with a SS amplifier. My take is that many digital based systems have too much gain that is then attenuated. Therefore a low gain preamp with a low sensitivity (high V = low sensitivity) amplifier can be beneficial.

Yes, the gain provided by a preamp is one thing, and often more than needed. How the gain is distributed via the volume control is another.