Hi_hifi - That's an absolutely fair comment--there is certainly a risk to "upgrading" older equipment. I wouldn't do it myself. To the extent I've done it, I've looked for people who seem to know the products involved really well, and put the job in their hands, let their judgment be in charge, and crossed my fingers.
Sometimes I've wished I could step into a time machine and go back 20 years and hear, with my ears today, the equipment I liked 20 years ago. I guess, in truth, I doubt that I would be so pleased with it, unless there had been some effective "upgrading". But I haven't really heard much of that equipment in stock form, it's true...although I have heard some of it, because it's still in the family. And, as I think about it, some of it I've still liked.