As far as calibrating, if the preamp has a HT bypass, you dont need to set the volume on the preamp anywhere, it is out of the loop. The way you suggested will work if the preamp does not have an HT bypass, you simply set the volume at an easily-remembered position, I use 12 o'clock, then calibrate your channel levels. Now whenever you watch movies, you simply set the volume to 12 o'clock and the levels will be set.
But you must remember to reduce the volume when using the pre to listen to music!
But you must remember to reduce the volume when using the pre to listen to music!