Best Bang for the Buck Upgrade

There are "Purists" and there are people who just have fun and enjoy the "Music" and not the "electronics....The Schiit Loki mini and Lokius can tailor, for a few hundred bucks, your system to make every album sound great no matter the quality of the recording...They are called "Don't say the words".........Tone Controls!!!!...I've been ready to sell different speakers and amps , but after adding the $149 Loki....I'm keeping them because I can mold the sound of each component....and it's fun being your systems "mastering man". ...I even bought a second one just incase the first one breaks. My system cost over $12,000 and this little $149 beauty changes the whole Hi Fi game....I'm getting the most enjoyment out of my music, Now.

Why don't you demo a power conditioner, like the P12 from PS Audio.  I have a P20, only because I have a very hungry power amp but I found a significant difference in sound stage size and micro detail when adding this to my system.  It also gives me a very black background.  I think they will give you a 30 day free trial if I am not mistaken.  I am in no way affiliated with PS Audio but I am a big believer in power regeneration when it is done correctly.  .  

I like the power conditioner idea. No need to spend fortune. Puritan makes good ones for under $2K.

Also, get a nice turntable and some records if you have the space. Some albums will sound better on a good vinyl pressing, especially Analogue Productions and Speakers Corner.

Simple reccomendation for your larger project: WyWires Platinum interconnects, comes in black or white. Benefits greatly from 200 hours burn-in. Their background is silent and the soundstage is deeper and better defined. A worthy upgrade at a reasonable cost.

Subwoofers do bring so much to the party if you can integrate them with your system and room well, even though your speakers are almost full range.

Room treatments, are a good suggestion.

Many recommendations here to attend to room acoustics which I fully agree with. Many enthusiasts who can't conceptualise what all this is about dismiss the idea and look to tweaks or a component change. Unfortunately without the treatment the room is taking control of the sound and for example any change of say DAC or cable is not that noticeable simply because the sound is taking long to decay.

Multi-subs have been suggested but the thought of having a bunch of huge boxes is off-putting, however a few much smaller and easier to accommodate subs will bring about a significant improvement as others have commented. A small sub can be tucked away behind the sofa, used as a side table or maybe built into an alcove or display cabinet. Once heard it is surprising how guys come up with places for them.

You mentioned a blanket across the glass slider helped. This is a good place for treatment but you can improve on the blanket which only acts as a narrow-band absorber. Consider a 2 or 3 curtain rail which looks the same as any other curtain but with 2 or 3 curtains spaced from each other and at different distances from the glass will provide an effect over a greater spectrum and also be more effective at doing it. Essentially it has now become more broad-band in its range. If you would normally use 2 drapes for a curtain use 4 so that they gather fuller and perform better. Can try this yourself with a big duvet etc. Good luck.

@ discopants: good post and greetings from AOS