Top 10 Snafus to avoid when building a good rig

Isn't it a big mistake to proceed from the premise that you are the absolute and the components are the variables? After all, our hearing and our moods and our attention all vary with time of day, time of month or time available.
I've found that listening for problems in my system guarantees that I will find some. On the other hand, by just taking for granted that your system sounds great and ignoring those who disagree, you can save a lot of money, frustration and anguish. It doesn't really matter whether your system results conform to an abstract standard or a consensus value assessment. If you decide to like what you have the game is over and you won. There is no absolute in sound. The entire industry is supported by your dissatisfaction. Whether or not you choose to be baited into that scheme is up to you, but no one but you should be making that decision.
If you want to be happy, go ahead and be happy. Don't let reviewers take that choice out of your hands.

using a mortgage or home-improvement loan for major upgrades

I strongly agree with Douglas S's post.

Macrojack makes a very good point. In the current issue of Stereophile one of the writers states that "it's good enough" is the most dangerous thought in audiophile land.

The only way I know of to build a system to one's satisfaction is in-home trial. Not always easy for a given component and even when available, does not always allow enough time to live with the component, 'dial it in' (by making other system changes including set-up in room). I think I have pretty 'quick' ears in discerning sonic differences resulting from a change in component or wire, but even if you can isolate the particular product's sound in another system by eliminating the variables, it isn't going to tell you how it will sound in your system, in your room, with your components.
I don't know that there is any 'easy way' to do this. It is one thing if you are building a modest system, and your expectations are 'good sound' (whatever that means to you) and once bought, you are pretty much going to leave it at that, and quit fiddling.
But, I've been around this game for decades, and like others, have fallen into the trap of listening to the gear, not the music, because something is 'lacking' and I want to achieve some incremental improvement. If my real love is endless tweaking and upgrading, fine. But, to be able to sit back, without audio nervosa, and enjoy what you have (and assuming you aspire to something that can give you the verisimultude of real music at some level), you are going to have to do some work to get there. That may mean trying and rejecting components after living with them. Buying used, because the tariff on brand new is too high. And recognizing, as others have already said, that no one system can do everything well.
So with that lengthy preface, I guess my list of things to avoid in system building is:
1. Believing that any one system can do everything well, on all source material. (Ultimately, if the system is at a pretty high level, you are a victim of the source material, how well it is recorded and mastered, not the playback gear).
2. Believing that any one component is going to make a night and day difference in an otherwise well thought-out system. We are building a complex system from individual components, usually from different manufacturers, wired together with cables from yet other manufacturers. That is, it is a 'system' and has to be treated as such.
3. Believing that costly components allow you to ignore best practices in room set up, a-c power and the like.
4. Being unwilling to experiment with set up changes and small tweaks that may not be terribly costly. This requires more time and effort than money.
5. Not being able to enjoy what you've built- which is a means to listen to music, not an endless quest for absolute perfection, which is virtually impossible.

" In the current issue of Stereophile one of the writers states that "it's good enough" is the most dangerous thought in audiophile land."

There is a big difference between the audio sales guy who asks questions and actually takes time to understand what you have and what you are looking for and the guy who works based on the assumption that whatever he sells you will be better.

There are plenty of both types around.