WILL IT MAKE A DIFFERENCE?

I believe it's mainly the room.. and also possibly speaker placement. You can try toeing your speakers out slightly. Imaging may lose some focus but it should balance the HF response. You won't be able to effectively 'roll' equipment until you have these things right.

You may then also try DAC or streamer filtering settings, if it has them. This will be subtle, but can help somewhat with fatigue.

I did insert a tube preamp between my Class D monoblocks and DAC (which works great driving an old Aleph 3 direct, but my DAC driving the monoblocks direct with no preamp.. while detailed was quite fatiguing). The tube preamp worked wonders.. midrange bloomed, the soundstage gained depth and coherence.. and this made the system listenable for long sessions with very little fatigue. It took a lot of experimentation rolling expensive 6SN7's before I found the right ones however.

That said.. driving a Pass Aleph3 directly with the DAC sounded the best.. the most coherent and organic, and with the lowest noise floor.. none I could hear basically. My DAC's output stage was designed for this.

Back to the room, one thing I have also done (& my room is a disaster.. very asymmetric with boundary issues on the right and open to the left and behind), was to fabricate stepped speaker baffles out of lamb's wool panels to crop the dispersion of the midrange and tweeter and also mitigate cabinet reflections and diffraction. Basically the same thing Dunlavy used to do with his SC series speakers. It was quite effective at cancelling reflection issues and improved the sound stage immensely, and this perceptively gave the sound a more believable, more organic presentation. I could listen 'deeper' into recordings, suppose I could say. I've read these baffles should be made of actual lamb's wool, and not synthetic or felt. I used "1/4 panels for the base layer, and "3/8 for the top layer. This is great if you listen primarily in the sweet spot, but if you wander around the room while listening, large plants, curtains, rugs, etc, might be preferable.

...one more thing.. about going all tube. I used to use single-ended zero-feedback Class-A tube mono-blocks in my system.. 80wpc. The top-end finesse was refined.. silky, they imaged great, but they never had enough drive for me to believe the sound as being realistic. The sound was a bit ’slow,’ and I’d attribute this to a lower dampening factor (compared to SS) and the fact they didn’t double down into lower impedances. That said, my speakers were not particularly sensitive and did dip down to 5 ohms, and many tube aficionados here know what they like and are probably using much more sensitive, tube-friendly speakers, but with this also means other compromises like non-linearity. For late night listening with a glass of your favorite beverage.. all tube is fantastic, but I’m advocating for the tube preamp (preferably one that performs well with the fewest tubes possible) merely as a way to season the sound for the better after you sort out the room, speaker placement, etc, and once you have that, with a tube preamp you still may have to roll. Many tubes I tried (esp stock) weren’t acceptable in terms of bandwidth, sound staging and being low-enough noise. Also, many excellent NOS tubes just aren’t available anymore, and you will need a dependable supply as they wear out. That said there are manufacturers of new tubes which perform better than 10 yrs ago, but the newer 6SN7’s I rolled in my preamp could not compete with my NOS picks.

There is also the notion of going to a minimalist tube buffer stage. A simpler cheaper route.. but I’ve not tried them.

It's your DAC dude.