Question on component impedance mismatch

Or, at least that what I think it is--a mismatch. I have a M900U Luxman amplifier fed by an Audio Research LS27 preamp which is fed from a  Bryston BDA2 DAC. The Audio Research has 3 gain levels and I use the lowest one. Still, when streaming sometimes position 2 or 3 on the ARC is too loud. 

I If I bought in-line attenuators, those little balanced plug in deals where would you place them? At the Preamplifier DAC input connections or the Amplifier input? Roughly what amount of attenuation would be reasonable? 

This is not such an issue when I am cranking the music up high, but when it's evening listening with my wife we've even had it on position 1. I think the volume knob goes up to 103!

I love the sound of my components, just would like a more reasonable volume adjustment.

Thanks for your comments.