Once I get something dialed in, I leave it until it dies. As such, I don't recall anything subtle. The only things I remember of any notable increase in SQ was large, like when CD hit the mainstream. That kind of set the bar for memorable, audible improvements.
Once my friends and I started growing up and many of them just dropping out of hi-fi altogether, people around me, who cared nearly as much as I do, were, and still are, far and few between. This changed my audio habits to a more selfish, studio type arrangement. The ambient byproducts to the rest of the room/house, are still better than what those who otherwise care little, are going to hear anywhere else. I basically have a busily furnished near field end, of a long rectangle, with a jug handle hallway that miraculously traps wayward bass at the opposite end.
The only exception would be, opening doors to other rooms, making my space effectively larger, or smaller. But these differences are lost on me 5 mins in, as with many others, including more drastic ones such as changing out to totally different amp types, and even some speakers.
