inktoxicated

trying to set amp gains to match the headunits output voltage. my processor has a voltage gain dial from .1-2.5 volts. obviously the system gets louder when set to 2.5 but then i have to turn my amp gains down. i dont know where to dial these things in. should i keep the processor on max so the amp gains are towards the middle or should i set the processor on lower so the amps gain are nearing max. both ways kind of make the syteme sound the same just dont know what is right