Room Treaments - Where To Begin...

My wife and I both heard an improvement and curiously mostly in the lower end, where it seemed like my speakers finally had some depth in some bass.

Yes!  I have written about this often.  Clean up the mid/treble and the bass rises from the depths. It's amazing how this can transform the sound of smaller speakers. It can make them sound huge.

@erik_squires yes, well I am certainly on board and can attest to it working better, I thought it might be from breaking up the bass energies. But on this I am still discovering what to do, well, at least I'm reading and muddling through it.

@fleschler about activated carbon filters, yeah I've used the Acoustic Fields QRD17 plans for four diffusers, and I'm deliberating building two or possibly three of their low frequency absorbers (I might even just break out the cash and buy them instead).
How much did you use? What sized room, and impressions?
I'd really like to know, sorry if I'm getting personal.

The best thing you can do, is to very precisely place your speakers by listening and using REW.

Take a look at the Before and after, with absolutely no room treatment. This living-music room is the most difficult room to make music sound good, vaulted ceilings, L shaped lots of little right angle little walls, a fireplace, and a lot of windows and skylights. On top the house is made with wood sticks, plaster walls, the wood floors are suspended, in other words a resonance box.

Here is the before and after, as you can see the bass was way too loud. Look at the dip between 200Hz and ~350Hz. 

Some could argue that I need more energy from 300Hz down, I will try new tubes to lower the brightness  and see what the tubes do