If you had to pick, what are some of the brands you think are most overrated or underrated based on what you’ve heard? 
Can be any type of cable
I would not comment about overrated, but for underrated, for sure is Audiokinesis speakers. The best bang for the money. As for the audio gears, Aesthetix and Atma-sphere are entitled for bigger acknowledgement. 
^^^^As good as Atma-sphere and Lamm offerings are sonically but what’s up with aesthetics...they are like electronics manufactured in 80’s :-)
Overrated: My ex-wives
Underrated: My future ex-wives
Of course, e have to include Bose, because we would not want any fans to think we can stand it!  TeeHee  Seriously, McIntosh. Sorry.  I would add Rotel, which I really do not like at all, but since I have never heard anyone say anything good about it, I can;t claim it is over rated.Also Maggies.  I have owned them and Electrostatics.  They have some of the same deficiencies, but the best soumd  from the 'Stats is far better than the good sounding part of the other.
Silnote definitively underrated
great value, great sound!!!!