Major mistakes made in assembling your audio rig

What types of mistakes (in your estimation)did you make in assembling your audio rig over the last 5 to 10 years??

For example,...."I should have spent more money";

"I leaned too heavily on reviews and/or the advice of others";

"I should have just stuck with separates and not downsized??"

"I just can't get the thing to sound the way I want despite much time and effort"

Based on any or all of the above.... Have you ever considered selling your system and starting over, or concluded, it takes too much time and money, and is a hassle.... so regrettably I quit
My first speakers were brand new Vandersteen 2ce and I didn't like them after few months of usage. The futher I heard them the further they stinked. Immediately after few months I bought used Aerial 10t that is on my system still for past 16 years and any attempt to upgrade them ended up keeping them. I also realized that most of the higher-end wires are only different by outside look just like designer jackets and shoes and replaced them with studio pro-grade ones that are not as pretty but darn lot cheaper. I only kept Kimber 8TC unterminated bulk wire.
This major "mistake" turned out to be a major lesson that would help me avoid other mistakes in the future. Many years ago, as a young budding audiophile, I made my first brand new (full retail) purchase, the AR SP9 preamp. After reading some rave reviews I was excited at the prospect of owning my first AR piece. I went to a local dealer where I heard it in what is still one of the most memorable systems I have ever heard: Snell Type Aiii, VTL, Roksan/Koetsu, SP9, MIT. I brought it home only to feel great disappointment because, even after a long break in period, it made (more accurately, it let) my system sound bleached out, thin and threadbare and just plain awful. After several days I took it back to the dealer who had agreed to issue a store credit. I thought that perhaps there was something wrong with this particular sample. In order to test it he inserted it into the same system as before and, once again, the sound was glorious. That was the moment when I understood the importance of system synergy and the idea that some gear simply does a much better job of getting out of the way and revealing the sound of the other components in the system. A great lesson. The store credit resulted in, among other things, my first vacuum record cleaner; another great lesson.
my way to avoid a major mistake was to find speakers that made emotional music and listen to them several times before purchase. Try to hear as many speakers as possible so you are reasonably confident in long term satisfaction.
since speakers are the one component that seem to have the biggest influence on a system's sound, start by choosing your speaker first.
In my toughest room acoustically, which is my wife's sunroom, it took me a long time to get something working well in there. Always either too much bass, too bright, or both.

Finally I ended up with a good solution currently in place using my Triangle Titus XL monitors on lower stands, only about 12" off the floor. This nails it pretty well. Higher up these were always too bright and not enough bass, whereas Dynaudio Contour 1.3mkII monitors or my smaller OHMs had too much bass.

I was tempted to try/buy other speakers to attempt to solve the problem on several occasions, but resisted the urge, determined to make something I already had that was good work.

It's always fun to play with new toys though, so I suppose I missed out on that, but I already have more than I can listen to as much as I would like, so can't complain.
The biggest mistake was trying to balance out a flaw in a component with a component that had the opposite flaw. I ended having to get rid of both components and replace them with components that did not exhibit major shortcomings.
Biggest mistake I ever made was going cheap on a digital scale to set up an expensive cartridge. Some cheap $10 weighs anything scale with a flat pan, instead of a $80 one specifically designed for stylus'.
Long story short, I snapped the cantilever setting up a brand new $5000 cartridge. 8 years later, I still have nightmares about that day....
"Major mistakes made in assembling your audio rig"

For those married or with someone - building it in complete
isolation of your spouse for fear of them knowing what u
spent. If something happens to you - it leaves the family in
a quandry.

You can break a few rules imo.
Its ok to sneak some stuff in .... even major stuff - the kind
that a value can be put on easily - i.e. by a dealer.
Just make sure when you sell something - they see it going out
the door.
this is important. you gain points ....
Include curtains in your room - they help with sonics .....and
to hide gear.
Not realizing how important cabling is and missing the beautiful music constrained and hidden because of poor cabling. Turns out the gear was wonderful, but the full potential lost by constraining cabling.
Inconsistent channelization and improper direction of fuses and interconnects. Also, not having the speakers close enough together.
Thanks to all for their forthcoming-ness ( is there such a word???)

Nevertheless, It is consoling to know that other 'philes have made mistakes. I once put the wrong amperage fuse in a new Conrad Johnson PV-8 pre-amp, only to observe one minute later smoke rising from its top vent, and the chassis toasted bagel hot.

The transformer had to be replaced, and worse I was talked into some mods on the pre-amp done for a grand total $650.00 plus local tax. At least, the mods lowered the noise floor as advertised by the tech.

Next, was my "interim retro phrase" while trying to decide on new speakers; so, in the meantime, I bought a used pair of large Advents with the shitty vinyl veneer. Though, to this day, I still believe, the Advents maybe one of most neutral and at times satisfying speakers I ever heard despite its terrible tweeter. I also learned that in the golden years of the original Advents tenure, most buyers were underpowering them. Unless, you wanted to invest in Phase Linear 400 or 700 power amp, and forego the Pioneer, Harmon Kardon, Denon etc receiver

During retro time, I drove the Advents with an Aragon 4004MKII 200RMS power amp, and they sounded very good

In retrospect, high-end audio is a demanding advocation; reading scores of reviews, and hours of careful auditioning components is a given. Too often, we are accused of listening to "equipment" and not the music, being snobs, being elitists, being anti-social. Nevertheless, those of us who prevail, know of the grandeur and the emotional high that a great audio system can produce, and therefore is worth the time and investment.

Maybe at our most petty and obsessed, we are just sound junkies, but the apprehension of well recorded music, and the personal satisfaction it brings, is not accessible by just walking through a room while music is playing, and humming.
Selling a 401 for $75 and my folks throwing away a 301 and Grace 707 and my 10 tube home made tube phono preamp along with a box of Mullards, Teles, Brimars and Seimens tubes.
Not upgrading my speakers sooner. In my defense, they were DIY speakers that I built with my mom, so they had sentimental value.

But I was spending money on accompanying gear that would have had much more impact on the sound if it went to speakers instead.
Can honestly say I haven't made many mistakes the last decade or so.
The system sounds wonderful , I'd be hesitant to change anything.
We can always look back and say, I should have went one more step up when I upgraded this or that, but then what would we do later ?
Sorry to quibble, but I'd rather say that I am and have been learning. Reading a lot of equipment reviews, more to glean a better basic technical understanding, has helped a lot. Engaging in a lot of Forum discussions with the likes of Ralph (Atmasphere), Al (Almarg) and other techies has really advanced the ball.

But here's a gripe. My interest in audio started about 40 years ago. Back then, there were a couple of high-end retailers who welcomed (or at least seemed to welcome) me and a couple of buddies to hang out and listen to gear and shoot the breeze. Also, I don't recall there were as many equipment brands to obsess about. Maybe there really were, but there wasn't interest either.

The oracle of the day was J Gordon Holt when he ran his underground Stereophile pamphlet. If JGH said something was good, it was good. But again, what did I know? I was a kid.

Well today it's hard NOT to make a mistake. Yeah, like many, I have bought and sold gear. I thought there was method to the madness.

Right now I'm stuck on speakers. I think I'm ok with my Paradigm S8s, but there's some other brands I'd like to check out. The thought of buying and trying and then ditching and trying again is a non-starter. My wife would skin me alive and frankly I don't have the energy. And like others have said, there just not that many high-end B&M stores around anymore, and for the one or two that might have some of the gear I am interested in, I am not comfortable "hanging out" like I did 40 years ago.

Bottom line: to call my progression a series of mistakes is harsh. It's more a steady process of figuring out what works and what doesn't, and the reasons why.
Having a $1k phono cartridge within reach of a 2 year old.
More of a parenting mistake than an audio mistake, but it still hurt...a lot.
Nice post; I agree with your take on the subject and feel that I am in the same boat. Some thoughts that come to mind:

I think that it is true that "back in the day" there seemed to be fewer choices, and many of those choices seemed to be able to tap into and give us that elusive quality that some of us refer to as musicality (like the sound of live; or, at least, having a good dose of it). I think that part of the reason for this was, ironically, because of the very limitations of the equipment. Contrary to what some fans of vintage equipment feel, I think that, overall, today's gear is infinitely better. The problem and irony are that as gear has become "better" (more transparent to the source) it also becomes easier and easier to put together a system that sounds poor (unlike the sound of live). However, it also becomes possible to put together a system that is far better than anything that I heard back in the day if one is willing to devote the time and research and deal with the inevitable mistakes? Not easy, considering just how many choices there are. Personally, I try not to stray too far away from the approach to system building that made it so much fun back then.
Not getting tube gear earlier! I would have saved a ton of cash if I didn't hold out!
1- Get speakers that work in your listening room and are not too big! Sadly, most floorstanding speakers need a lot of space around them to work well, and that's not possible in many rooms. Consider monitors with a subwoofer. This offers flexibility in dealing with the bass problems that plague many rooms. You can place the monitors where they sound best and move the sub where it performs best. And if that's not enough, you can adjust the sub's level and crossover frequency!

2- If you spin vinyl, get a good phono stage. The phono stages in even excellent integrateds are good but not great.