Consider a pair of vintage McIntosh or Marantz tube amps, if you can find a nice pair. You really can't go wrong with either. In any case it must be TUBES. Surely no SS amp 20 years or more hence will make the grade. There is just something about exposed tube gear that will always keep people intrigued thus maintaining and elevating their value. No speaker will have the physical allure or universal appeal a beautiful tube amp has. SS, forget it. Today's best will be superceded by tomorrows offerings and there is no visual attraction unless you consider the case which may have a "dated" appeal to some but still, heirloom quality? What could ever compete with the glow of a vacuum tube? It's always going to be cool and vogue and thus will maintain and increase in value.
Hey, want to buy an old Perreaux amp, about 25 years old. An old friend, who I haven't seen in years, dropped it off to me last Sunday knowing I'm into audio. He bought it many years back from his late audiophile brother-in-law who at the time upgraded to ARC gear. He can't get it fixed and thought I might want it. Thanks for thinking of me Alan, just what I need, a broken 25 year old SS amp. I guarantee it will make a great door stop. You think someone would ever use a McIntosh MC30 as a door stop?