Every piece of vintage Philips gear I have gotten my hands on has been exceptional.
I took me quite a while to find a post about Philips. That being said, their HiFi line of speakers, amps, etc are absolutely UNrated which I guess would be underrated on this thread. Also I'd add the Braun/ADS brand, even though many are huge fans of them, they are not properly "rated" given the all around quality that surrounds the product line, and how well they compare to todays products.
I NAD really overrated? While I am not an expert on their gear, are they not an affordable Hifi option for those on a budget? I mean not everyone can afford the McI's, Krells, Brystons, and the rest.
As for overrated brands being named in this thread, it's probably not fair to diminish a brands popularity and longstanding reputation simply because they are expensive. McIntosh has been around long enough to have earned their place in audio history, I don't have any, but would like to. As for Bose, after seeing all the speakers in for repairs at a local speaker repair shop, I was amazed at how many were Bose, the tech/owner said he could make a living on repairing and refoaming the 901's alone.
Overrated for me also would be the asking prices for vintage JBL speakers. I have some of them, but can't see paying what people are asking for today.