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
