Your single most significant purchase mistake?

A pair of Acoustic Phase speakers ($200) that I bought at Crazy Eddy's in NYC back in 1976! Large two-way boxes with a 10- inch woofer and a 1-inch mylar tweeter. Actually not bad - but not special! Sold them for half-price to a co-worker.

@sandthemall : good call on the Carver TFM15! I have the cb version in use in the front room system driving OHM Walsh Sound Cylinders. I bought the TFM15cb at Goodwill for $20!

The whole surround sound think, especially the final system, a Yamaha DVD player that was unreliable, Rotel Pre processer that never worked properly with volume that changed mid track lots of lights but no setting that was not awful, 2 channel power amp that was really quite superb and stayed as a stereo amp for 15 years until recently, a 5 channel power amp with no guts and 5 Kef speakers that apart from the centre, I still have but have no need for, were lumpy and disjointed. 

Funk LSD turntable… sounds lovely but it’s fiddly as all hell…..

I read someware that the i2s connection between a streamer and a DAC has the best sound quality. I wanted to get the most out of my fancy DAC so I went a head and purchased this 5K streamer with an i2s output. Little did I know that streamers in general preaty much sounds the same, plus I can't tell the difference between my $500 node 2i S/PDIF output and this $5000 streamer i2s output both going into my DAC. This was the largest mistake I made to date.

Lately, I tend to think that an all in one amp of the highest level, something like a darTZeel amp, can sound as good or better then seperates, costing about the same, looks better, and without the jungle of expansive cables dangling at the back on the floor. What do you guys think?