Your single most significant purchase mistake?

2 Solid-Tec Rack of silence, they flex and twist more than an overcooked spaghetti.

VPI signature, I tried to like like it, but never got me.

there.

Reference MM de Capo speakers. Everyone said they were great; reviewers and owners alike, so I bought a pair and hated them. They were soon gone.

Everything I ever bought from Rega. Never again. 

Emotiva pre-pro

Sold within a short time.  Lots of issues.  Sounded OK when it wasn't constantly switching "modes".

@stereo5 , it was a Clarion years unit (production run of 1992-1998).
I'll admit that Mc has built some "duds" over the years in an attempt to chase trends, but feel they hit the mark more than they miss it. My C2300 is certainly a keeper.