Not sure what to think

@asvjerry I think I followed your train of thought.

My explanation is that many who love this hobby just can't do much to the space their gear is in -- but they still want to tinker, opine, etc. It's a natural and laudable enthusiasm even if, from a scientific standpoint, they're really just wandering around in the dark, muttering magic words to others in the same situation. And, of course, in a problematic room, one can change things by changing gear, but maybe not as much as wishful thinking would like. I would never spend a lot of money on gear in a bad room. Waste of resources. Again, not to take any joy away from those folks, everyone is the conductor of their own orchestra.

Some acoustic spaces can be dealt with using digital correction, but there are limits. 

@hilde45 ...and your POV is basically parallel to mine, scary as that may seem..... ;)  One can only adapt or augment your 'average' living space with the various forms of treatments available to the point of:

1) SAF fading and replace with clenched teeth and long 'dry spells'
2) Friends and 'quaintance thinking your taste in wall art and geometric infill furnishings has been totally supplanted by an 'audio frenzy' difficult to comprehend.

Worst case scenario, personal history =  a 10' x 10' room with 10' ceiling, 3 doors, 2 windows,,,,in a rental home where that was the living room....😣

Even the bathroom was bigger.....but even more 'audio unfriendly'....*L*

Yes, DRC and even an 'gear downplay' wouldn't solve that...headphones, yes....but a set of small Chi-Fi (that wasn't all that available at the time) may have worked better or at all....🤷‍♂️🙄

'Imho'.... formed by experience, tempered by the commentary here and elsewhere about room acoustics, eq in general and DRC in specific.....
It takes me about an hour just to 'adapt' my sensibilities to another persons' audio tastes and array of equipment...given what may be played upon such, and notwithstanding the room itself.

Like most (I'll assume, but knowing full well the 'alt' definition of 'ass of 'u' & 'me'), I've selected that which fulfills personal present desires and needs at the price point I'm willing to hit.  It may not match mfrs., but it does what is expected...more if possible, but that's a 'cheap thrills +' at the end of the day.

In short, like many, I know there's always room to improve but for the time being, I'm satisfied...  Things come and go, but the current focus here is 'flexibility' over ultimate perfection.

Which, before and still, is in ones' own ears and mind.

In mine...it was when the THD %s' for 'mid-fi' and 'Ultra-Fi' started to get close enough to each other that it began to be a 'bragging point' v. 'practical, 'in use ' that I hit pause....

An easier train to board?  Or just boring.....? *L* J

@roadcykler @hilde45 

Could you explain the physics behind that contention?

Sure. All surfaces reflect to some extent. This causes wave interference, constructive and destructive, which is perceived as amplitude peaks and dips at different places and at different frequencies. This can be mitigated.

Also, all surfaces deflect to some extent. This causes the walls to bulge outwards on the compression cycle and cave in on the rarefaction cycle. Each flection is frequency and amplitude dependent, and of course adds and subtracts energy to or from the sound wave. This is perceived as a muddy and poorly defined bass response, and can also be mitigated. Note that this is why very few loudspeakers are made of drywall.

As if that weren’t enough, even a solid concrete bunker has a characteristic sound determined by the ratios of length to width to height. According to simulations done by the famous Cox, MOST ratios are just plain bad. A quarter are OK, and a few percent are good. It is instructive to compare Cox’s science with the recommendations of some who should know better.

The results are more complex if the room is irregular.

That’s why a good room will allow most good systems to sound better than most poor systems. So look to your room.

non-sound treated room...

I stopped reading here....😅

It’s very possible your “no special cables” are bad enough that they have obscured any differences in SQ between the two preamps. Cheap freebee cables can be bad enough to do that.

You should have at least heard a change in character in the sound of instruments or voice. If not your cables than you might be lucky to have hearing that is insensitive and don’t have to spend lots of money on audio.

have you tried other changes in your audio setup and heard differences?.