I don't *think* it matters whether you have individual channels turned down and turn the volume control up vs. individual channels turned up and turn the volume control down a bit...
... but just in case I usually shift all the settings up or down as required so that they aren't too far from zero. For example, last time I played with the "ez-set" on my HK receiver I ended up with something like 0 for mains, -4 for center and -10 for surrounds (they're really efficient albeit crappy sounding). I shifted everything up 4 dB to give +4dB for mains, 0dB for center, -6 for surrounds.
I'm pretty sure this doesn't make any difference but it seems "tidier" and I don't have to re-learn all the volume control settings for different inputs and different disks
