Your single most significant purchase mistake?

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? 

@Jasonbourne52

That's a great find for $20! Mine is the TFM-15CB too.

On eBay a few years back I bought a TFM-35 NOS in the box for $450. No pictures, just the outside of the box. This I had compared head to head with Don Sach's Kootenay. And, yes, the Kootenay was the better with more body...but the Carver had a slightly prettier top end. The Kootenay didn't murder the Carver...in fact, in a bizarre sense, they sounded somewhat similar. They were both running through a Don Sachs preamp. Also the Kootenay had only 50+ hours on it and would surely sound better in time.  

@cleeds & other Aurender N100H folks: I have had similar troubles, although to date Ari has got me back & running. Question: knowing this will be just a temporary component on my digital side, WITH WHAT DID YOU REPLACE the N100H?

I have an N100H sitting in storage. I had problems with it too and as you just said, every time I turned it on I never knew if it would "see" my router or not. I replaced it with an Aurender W20 and it has been a complete joy to use. Never a single problem finding the router. Ari at Aurender is an excellent dude. Whatever he is being paid, Aurender ought to double it. I got to know Ari too with my N100H. With my W20 we are now strangers. Btw, the SQ with the W20 is night and day to the N100H.