Remarkably better sound possible with just 1 system component change?

That’s a cool room! I’m working on something similar, and yeah it will also break a lot of acoustic room treatment rules.

Pretty much everything has been said, but I’ll add my 40 years of experience here:

(1) At the level of gear you have, a "remarkable" improvement is going to be hard to come by. Synergy between components is important, and that can’t be taken in a single step. It requires auditioning gear within your system from a dealer that trusts you’ll bring it back or pay for it. Andy at Saturday Audio Exchange has let me audition endless pieces of gear and it’s a lovely way to build the system. But anyway, my main point here is that improvement takes time and work and is thus usually incremental, not dramatic.

(2) You would benefit from acoustic modification to the room. But it doesn’t have to disrupt anything - you need to take it as a challenge and get creative. Get the Metallica logo printed on a giant set of drapes and then you can take down the poster...no loss then. Bass traps in team colors, etc. You want remarkable improvement, then you’re going to have to put in some remarkable effort. Good audio isn’t $$.

(3) You said you’re not looking for more bass, but I am a big fan of REL subs for this reason - they are not really tuned to make explosions in movies move your couch. They add "air" to the room and I often find the biggest impact of the good REL subs is on the vocals. Part of the REL goal is to pick up the frequencies that create hints around the physical space where the music was recorded, and it can sort of take you away.

(4) If you already love your system at high volume and it is low volume where you want improvement, this you might be able to force without finesse by adding a small integrated tube amp and near field speakers near your seating area. It might be hard to extend out the sweet spot from your main system.

(5) It doesn’t look like you’ve placed your seating area to be in the sweet spot, as above, or at least your room implies you may be listening from a number of different stations around the room. Not that I think gear is your issue, but dipolar or bipolar speakers tend to have a wider dispersion of listenable sound. Consider a pair for when you’re not sitting still in the sweet spot.

(6) Source can give dramatic upgrades too. I don’t know the Lumin gear but I do prefer the non-MQA Qobuz sound.

(7) One more idea just for fun: get yourself set up with a reasonable 5.1 system and start collecting 5.1 channel DVD-Audio, SACD, and Blu Ray disks. Now that is a remarkable improvement, and with just the built-in room correction on your AVR, it somewhat defeats the issues with your room.

Sorry for the tome, I guess not everything had been said.

Oh yeah, and good weed.

@cycles2 I also have simple < 75$ fiber optic converter in addition to ethergen. I have seen significant improvement in this “switch”. I don’t have lumin x1, but with my streamer, using fiber optic + etheregen was much better than fiber optic alone. It could be system dependent and there are no absolutes: I think it is worth trial, as they can be returned back in 1 month if you don’t see benefit. Also to OP, adding a good subwoofer (preferably 2), will be a huge improvement. Good luck.  

Would speaker podiums be of benefit if speakers are on a concrete floor?

A lot of suggestions offered. Unfortunately the bulk of them will NOT bring about a significant improvement. In fact unless the room acoustics are sorted the small but worth while potential of some of these suggestions will be lost in your room which leads people to refer to some as 'snake oil'

To get to hear the sound your existing components are capable of requires that your room allow you to do so. Changing cables etc. in your room as it stands is futile as some have mentioned. With sound left to propagate in your room unchecked, causing smear, congestion and lack of detail you will not be able to fully appreciate what the already mentioned Max Townshend platforms can bring to the party. Ditto with cable lifters, AC filters and so forth.

A bit of theory but let me first relate what a stubborn mate found out. In a small almost square floorplan with no carpet or drapes and very little else he kept upgrading to progressively more expensive cartridges and was getting nowhere. And he never will. He has upgraded amps and speakers at great expense but not achieved much. I brought round a bunch of rockwool panels and distributed them without too much fuss. It was merely to demonstrate what was possible.

It transformed his system. I do not say that lightly. He and is ever suffering wife were stunned.

I have copied and pasted part of a post of mine from another forum:

For whatever reason, treating a room is low on the priority list or just completely ignored. The Royal Albert Hall in the UK had a big problem with the dome. People joked about the echo, saying: you can hear any piece twice at the RAH. After many attempts they resorted to dispersion by installing large 'upside down mushrooms.

My point being, all rooms need acoustic treatment and the smaller the room the more important it is. All it takes to tackle this scientifically is to download for FREE the very useful REW and buy, for about the same price as modest interconnect cable, a microphone. Online you can find, also free, programs that will identify the modal issues. So you let REW produce a waterfall plot of your room. This will show exactly where the peaks and nulls lie and also the amount of time the sound takes to decay.

How long should that decay be? Good question. Work out the volume of your room and find online a table that provides the correct T60 for that size room. T60 is the time it takes for the sound to decay by 60dB and for my room is about 400ms.

This is not expensive, provides a bigger 'upgrade' than any component swap and is great fun. When I first did this I found it to be quite exciting to watch the waterfall plot reveal that the peaks were being tamed and the nulls started filling in. Bass traps are needed to reach the lower frequencies and as I added them I noticed that what was previously a partial or complete null start reaching up to the mean amplitude.

For anybody reading this not familiar with peaks and nulls on a plot, a complete null is zero music. When this fills in from preventing bass waves from combining destructively you now get to hear parts of the music not previously heard. When preventing bass from combining constructively you tame the peaks which lead to one-note-bass. On my system I can hear all the detail of Ray Brown' double bass and its wonderful.

No amount of money thrown at bigger better amps and/or speakers can provide that music being cancelled in the nulls. It's gone and you ain't getting it back unless you address the cancellation problem. And no Sir, EQ can not bring it back. Partial nulls can be boosted a little but this will not help the power response. Some nulls will require maybe a 20dB boost but where will your power come from. A 12dB boost will need power doubled 4 times. So from 60 watts to 960 watts but of course there are not many domestic speakers that can handle 1Kw and even if they could would just cancel those particular frequencies with the same power!

Small scraps of foam, beach towels and bookcases just physically can't achieve this unfortunately.

As you can see from my comments above EQ can not in any way manufacture the music missing in the nulls. Partial nulls can be boosted but only a little before the amp runs out of power. Those Lyngdorf type units can help only if the main acoustics are reasonable. It should be obvious that the unit certainly can't take a group of frequencies and reduce its decay time. Correct room treatment can.

Also if you are not interested in the effort to measure then simply absorbing at the first reflection points and adding a couple of bass traps will make a significant difference. A DBA will improve things further.

This post is getting too long so I'll finish by saying I can see an easy way for you to install some treatment that can benefit the stereo side and home theater and without it getting in the way. Simple and adjustable.

Let me know if you are interested. I have spent considerable time with another member emailing back and forth only to get an email from his wife : "Look here, we're not interested"

A lot of suggestions offered. Unfortunately the bulk of them will NOT bring about a significant improvement. In fact unless the room acoustics are sorted the small but worth while potential of some of these suggestions will be lost in your room which leads people to refer to some as ’snake oil’

Many audio devices injustly qualified as"snake oil" are not working well because of the lack of controls in acoustic of the room....

No upgrade rival acoustical controls....

Electronic design upgrade dont lit a candle compared to acoustic controls in audio.....

But all magazines sell new "improved" electronic design not acoustic method....

At best they speak time to time about passive acoustic materials but passive treatment is NOT non electronic active controls, and these 2 are NOT electronic active controls either and must not be confused....The road is not a simple linear way....Ears reign supreme here, governing these correlations between passive treatment and the two kind of active controls; measuring device are only tool under ears supervision....

On my under 500 bucks system i can hear the vibraphone aural tone hues changing dynamic decay with each passing tone and the sound dont come from my speakers, why?

Not because my amplifier is a Sansui, not because my speakers are Mission Cyruss , not because of my Dac....They are only good products among many others....

Because acoustical controls are in place.... But it is VERY important dont forget mechanical and electrical controls.....Unbeknownst to most these 2 controls are on par in transforming power with acoustical controls.... All these controls i called audio system embeddings controls 😊

I only underline here the importance of the last post by lemonhaze....