Lowering gain of power amp is a good thing. Overall gain from the source to speakers will be the same, but spread of the gain will change. More gain will be allocated to pre (quieter environment) than to power amp (noisier environment), not to mention reducing noise pickup by ICs (higher signal level).
I don't know construction of Parasound, but even if gain is fixed and you just lower the signal (volume pot), the level of the signal entering the box will be higher (better for S/N). Yes, engaging Parasound pots puts them in the signal path, but reducing authority of preamp's volume pot (max power=wider angle) is good. I would do what rodman99999 recommended, unless you can hear audible difference.
I don't know construction of Parasound, but even if gain is fixed and you just lower the signal (volume pot), the level of the signal entering the box will be higher (better for S/N). Yes, engaging Parasound pots puts them in the signal path, but reducing authority of preamp's volume pot (max power=wider angle) is good. I would do what rodman99999 recommended, unless you can hear audible difference.