I don't usually buy really old stuff but there are brands from the 80s and 90s that kick ass. Often you can often get it for the price of normal new stuff. So you pay a normal price and get something that would cost 2-4 times what you would have to pay new for the same quality. Most of the time it is just amps because speakers have improved quite a bit over time IMO.

My favorites:
NAD amps sound great and are incredibly powerful compared to the ratings
ADS car amps and some speakers. Just a different world.
Klipsch speakers

I think some of the newer A/D/S stuff is all right. I am hoping to use an old A/D/S power plate amp with ~1000W (I have seen an 800W one) if I can find one cheap enough with a Resonant Engineering XXX 12" or 15" sub.