Hi David-
 As I understand your message, my personal method of tweaking sound
systems start at the electroacoustic interface, and in sound systems,
that is really a distinctly different system, and has to be considered
FIRST. One one side of the line, you have everything that you want to
feed the power amp/loudspeakers which is selected FIRST to deterime
coverage issues and having large enough/enough drivers to adaquately
cover that area with even sound, then you can look at how much power and
amplifier channels one needs to appropriately adjust these levels,
assuming no overworked drivers or amplifiers for sufficient headroom. At
this point, it then comes down to what you want to feed it....
Now as far as gains go... I almost always set levels at their nominal
levels, allowing for headroom and keeping the noise floor low. I design
the amplification /speaker system to be expecting to get a line level
signal where 0dB is  referenced to full output of the sound system less
headroom, so I always know just where things are in relation to the
sound system output.
At that point, then everything is handled from the program end of
things, the amp/speaker system is a backburner item, now. Plug in your
program sources and get creative!!
I consider all crossovers/electronic crossovers/frequency response and
transient protection to be within the domain of the amp/speaker system,
so that everything appears flat in frequency response to the program
sources.
Then a lock goes on the adjustments for these things as "no one" is
supposed to play with this EVER!!! Mucho testing with expensive test
equipment verified that there was no better way to make these
adjustments, no user servicable parts inside.. Keep your hands off or
you loose fingers.. That serious.... unless it is a portable system, and
then you get to tweak from loadin until showtime trying to make your
system work in this weird room with that monster flutter echo due to
poor room design..
Oh, if we REALLY want to do a first class job and have that sound system
sound so primo... FIRST, the room needs to be considered that you are
going to put the sound system into.. A first step that many home stereo
and even most project studios hardly ever consider. Often times, it is
an afterthought in the design of facilities.. amazingly enough, since
they ought to realize that people are going to collect in these places
and they are so spoiled by what they hear at home that they are
expecting at least that good out of the system in this church, concert
venue, etc..
 Matching components for sonic preferences, electronic compatibility,
and the all critical site tuning of the system can take considerable
effort. time AND skill. On the other hand, to get an acceptable sound
most anyone can do with almost any pile of equipment.
Hopefully, after all of this effort to produce good sound, hopefully,
you have something worth all of this effort to put through this system!
-> This started me to thinking because I have always used the input
-> volume controls on the amplifiers to match the various speaker
-> volume's in a system (before EQ), since different speakers have
-> different efficiencies.
Yes, that basically works, as far as you take it. Additionally, you need
to consider the listening position, the distance to that listening
position, what the kind of source and whether it conforms to the inverse
square law or not (some speaker systems DO NOT conform to this). Now, if
say, you wish an average of 95dB at the listening position,  and you are
so far away from the drivers, you will need to feed the the speaker
with x number of watts on an average to get you to that level without
exceeding the headroom or capabilities of the power amplifer. This may
require a considerably smaller amplifier than you are using on that
speaker, and maybe a smaller gain block should be considered to give
that level without loosing gain and adding noise at undue cost to have
a monster amp loaf.
 Much of the above is my own philosophy that I have used in many
successful installations over the years. It is ispired by Don Davis
(SYNAUDCON), who turned me on to many other great folks, and William
Dilly of Spectrasonics, Inc., but there is a little me in that
philosophy, too!
Bonnie *:>
--- QScan/PCB v1.18b / 01-0249
---------------