References available on real life room "tuning"?

Why not start by subtracting pieces of furniture and ornaments
and things on the wall. You might be able to hear a difference by
addressing the "mess" this way.

Attitude is important, too. You could suggest to your partner
that this is just an experiment, and encourage her to keep
an open mind while you explore different possibilities, together.
Set aside a few hours for this project, and keep it fun.

Change the positioning of your speakers and try a new location
from which you listen to music.

You can also look at pictures of other systems, on this site.
Jim Smith's book, "Get Better Sound" is bound to help, too.

If you find you have need to absorb or diffuse on the walls you can wrap foam or diffusing panels in attractive fabric.Carpet tiles may work too,check out "Flor's" website.

RW Have you talked to the Marigo fellow? He has good rational behind his window dots,is an avid and knowledgeable music lover, and offers his product with a no question guarantee. Have you tried them yourself? If not you might watch shooting off at the mouth when you have little but prejudice to share. And even if you feel obligated to share you perhaps you can find a way to do so courteously.

Finding different ways to change or eliminate the problems isn't the problem at the moment. Determining what and where to do is. I thought with the incredible amount of desire for better audio there would be a mass of literature, and maybe even some websites dedicated to the subject.

I'll look up Get Better Sound and take a gander at it.

Natural fibre fabric behind the speakers. Try thick wool carpet pieces.
Some kind of sound absorption at the first reflection point.
Nice comfy sofa to absorb sound at listening position.
If your couch is positioned against the back wall, all the better as your head is close enough to the back wall for your brain to not process reflections (it's what they do when in caves-get against a wall to eliminate echos and fix on actual sound source).
Hope this helps.

All the best,
Nonoise