Easy one first, the Synergistic Research Master Coupler is totally the way to go. I got my first one nearly 30 years ago, still use one today, and mine is a pretty darn fine dialed in system.
https://systems.audiogon.com/systems/8367The better SR are definitely worth the money. Something that cannot be said of the competition. So if you find a used UEF or Blue or whatever make an offer, you will be pleased.
Look through my system page, read the descriptions. I have a lot of different SR and have used many more over the years. This is because of having compared a lot and learned SR value per dollar is higher and more consistent than anything else, and I am a value buyer. If you buy based on anything else you may prefer something else.
Every single inch of wire matters. The biggest improvement by far is going from the freebie patch cords and rubber power cords that come in the box. Those are all rubbish and meant to stay wrapped in tape in the shipping carton along with the manual stored up in the attic ready for when you sell to the next guy. When you swap out your rubber for a Master Coupler you will know what I mean.
One of the bigger obstacles to better sound is all the advice that is out there from people who cannot hear very well. Or worse, people who refuse to hear anything that cannot first be explained. Its like they would look at a blue sky and refuse to believe it is blue because air is clear and space is black and the sun is yellow so how can the sky be blue? You can say looks blue to me all they will do is question and quiz and eventually insult and bully. The sky is blue. Deal with it.
So yes indeed you heard it settle in and the process is so universal and so consistent across so many different components I can tell you from here a thousand miles away and without even knowing what it was, I can tell you what you heard.
You said similar to new IC which sound thin and unengaging. New components always sound like this. The fundamental characteristics of the component are there from the beginning. But leading edges are emphasized, there is more etch or grain, especially with upper harmonics, and fundamental tones are weak. Its as if you are looking at a skeleton. You can see the shape and all the parts. Then over time the fundamental body of the tone fills out, the sound becomes fuller and more palpably 3D, eventually reaching a point where you realize the sound is much more detailed than in the beginning, but yet also much smoother, more liquid and natural.
This whole process can play out over anywhere from several hours to weeks or even months. But always the changes are the greatest and fastest in the very beginning. The same thing happens every night by the way. Even with everything warmed up still the first side never sounds as good at the beginning as by the end.
If you get a Master Coupler, even used it will still go through this settling in process just the same only less and much faster.
