Which components are "stupid good"?

"Exceptions don't render generalities irrelevant".
This sounds like spoken by Roman senator.
In my experience, Custom Power Cord Co Top Gun power cord certainly qualifies as "stupid good". I bought it here used for $87 ( I think, it was $400 new) and it made such a big improvement with my Audiolab integrated. Then I bought another one for $125 used and it took my Acoustech phono stage to a significantly higher level.

I think what PM means is he is wanting our views on inexpensive(relative) audio equipment that is much better than it's retail price should allow. Everyone knows there is expensive(relative again) equipment that sounds good.

I don't know why I didn't put this on the first time, but:

Cary Audio SLP98p, great piece.

Can be found relatively cheaply on A'gon used, and it really sounds sublime. Anytime a piece of gear has been around this long, has that kind of longevity, it's bound to be pretty good.

I love mine, never have a desire to change out.

The Cary should sound good. It's fairly expensive.

mhdt Constantine DAC.

I'm not sure what more one could expect from a DAC than this delivers, short of jumping perhaps into the big buck DCS gear.