Have you tried using the volume on the Dave and skipping the pre? It's an amazing piece of equipment and should do well.
Preamps
I'm not unhappy with the Jeff Rowland Corus preamp, but I don't know what I don't know. I'm currently looking for a solid state preamp with HT bypass to compare to my Jeff Rowland Corus preamp. I would like suggestions below $15K new list price to listen to. I have a Jeff Rowland 625 S2 amplifier, Antipodes DS GT music server and Chord Dave DAC.