I find the opening question curious. I have never really wanted to be upgrading. It is just that I could not afford what I really wanted at the start (or anything even close), and so I settled for something much less, and over time upgraded when I could afford to do so, and have upgraded to a point where I am satisfied, and have no particular interest in upgrading, because it would be too expensive, and give me very little improvement. Upgrading for the sake of upgrading is something I have never wanted to do. The point of the gear was to have good sound, and if I could have had perfection (or near perfection) from the start, I would never want to upgrade.
Some of the upgrading I have done was through buying and selling used gear, and in doing that, I usually made money rather than lose it, which is why I was able to do some of the upgrades that I did, and also why I did some small steps rather than doing more saving up for bigger improvements (buying new, making small improvements, over and over, costs a lot of extra money, so one would typically be better off saving up for a big improvement instead).
If I had been rich from the start, I probably would have purchased the
Infinity QLS-1 when they came out, along with appropriate amplification and sources. (That would have cost as much as a
good new car at the time.) Whether I would ever have felt the need to upgrade them, I do not know, as I don't really remember what they sound like, since I have not heard them since the 1970's. At the time, they seemed to have bottomless bass, certainly the deepest I had ever heard in a speaker, and the treble seemed light and airy and delicate, yet as forceful as it needed to be. And, being a line source design, they sounded good sitting down or standing up. I would like to hear them again (in original condition), because I am curious about how they sound, and am curious what I would think of them now. At the time, they seemed to be close to perfection. Certainly, they were the most full-range speakers I had heard at the time, and that might still be the case. But I am not seeking to buy them, as I am satisfied with what I have, and have deeper bass (than the QLS-1 is rated for) now due to using really good subwoofers.
At this point, I only buy things when I need to replace something. I recently had my Blu-ray player fail (it still plays DVDs, but usually not BDs), so I have ordered a new one. (The new one is region free and PAL capable, so it is an improvement in those ways.) Before that, I had not purchased any gear in years, because I am pretty satisfied with what I have. I will want to upgrade my TV eventually, but given that the old one works perfectly, and is the best TV I have ever owned, I am not in a hurry to do that. But, when I eventually buy a new TV, it will be bigger and better than what I have now. For the audio side of things, I am satisfied with what I have, and will only buy things if I need to replace something. That would still be true if suddenly a million dollars landed in my lap, as I would rather spend the extra money on other things, like more expensive scotch and wine, maybe a nice vacation, etc. My audio gear is really good at this point. Sure, it could be better, but not much, and I would rather not spend thousands for a tiny improvement. Of course, other people may be less satisfied with what I have (just as I would not be satisfied with some of the things that others regard as "the best"), but their preferences are irrelevant to my choices, just like my preferences are irrelevant to theirs.