asp307Hi, I noticed that you want to keep your Rogue Cronus Magnum Integrated (that has high gain 12ax7 input tube), but you want an external preamp.
No one bothered to check that your Cronus integrated only has pre outputs, but no poweramp inputs, to make it serve as a poweramp, as there are no input rca's for an external preamp.
So if put an external pre into the aux input you will have way too much gain especially with the Zu speakers, and two volume controls and two balance controls to deal with, with so much gain you may not get passed 8 o’clock.
http://www.rogueaudio.com/manuals/Cronus%20Magnum%20II.pdf
Cheers George