I will warn you that Koetsu over estimates the output of their cartridges. The Black is probably closer to 0.42 mv.
When I switched from a Koetsu Rosewood Signature (with a supposed output of 0.6mv) to the Shelter 90X (0.6 mv), I got an increase in volume, albeit not a lot (maybe 2-3 db).
However, I agree with you that it is convenient to have the volume control match between the two sources. I hated switching from LPs (where the volume control was at 12:00 for normal listening volumes) to CDs, (where the volume control was at 9:00 for normal listening volumes), as I always seemed to forget to turn the volume down first.
(It was kind of like getting into your car in the morning and the radio is blasting, whereas last night when you parked, it seemed okay.) :-)