Which area of components to spend the most $ on? Boy I was wrong all my life!

Ask yourself, what factors in my listening environment remain constant regardless of any component changes you may make in the future. The answer is probably the power coming from your wall and the room itself. If we provide appropriate power (components can be fussy) and improve the cleanliness of our A/C, we can make any component sound better. The influence a room makes is well known, so why do we think putting the horse before the cart is the logical procedure. 

One of the most important considerations is the length of time your investment will be retained is can be considered with respect to changing technology. 

 For these reasons I feel that the most significant investments should be placed initially on speakers and amplification as these technologies are not as   Quickly evolving.

Cables also make respect to investments. For digital front end I would then get the best possible however always keeping consideration the fact that I will probably upgrade at some point

Where to put your money is always important to consider when you first set up a higher end system, however once your first "true" higher end system has been purchased and and balanced properly based on budget then the merry-go-round starts for many and the notion of front end vs. speakers or any other components does not fall into a tight set of rules. If your budget was high enough initially then the front end might be sufficiently high to warrant the next upgrade being the speakers or if you bought an integrated amplifier you might want to then purchase an amplifier and preamplifier, so after that first initial "big" investment you made in your first stab at creating your first true high end system then you go with what you perceive would be the smartest next step in moving into the merry-go-round phase of upgrading.

What a Thread...!
First thought: it's generally conceded that speakers have the
toughest job - transducing electronic energy to physical. It follows
that here is where the "soundpath"is more likely to degrade. The source starts the journey at 100% (?- or less). All the stuff that follows can't improve, but will likely alter the signal to some degree.
Speakers are the component most likely to add or subtract the most:  They have the toughest job.
Second thought: Audio experience has more to do with what
you hear than any math calculation. Seems as tho' some folks work
back from their experience to justify their %s as universal.
Third thought: Too few responders have fully qualified their observations - it's THEIR sound: their equipment, their room, their ears and their brain (memory). Lots of variables here. Too many to attempt to allocate a hard and fast priority to certain components alone for every listener.
Personal comments & suggestions make for good conversation, but they are only that - personal. 2Psyop has it right and bigbobbydmoney's first sentence covers it all - simplistic, but true, non-the-less: "Building a system is a process based on one's listening preference and ears". (Oh - and the brain!)
Bo

The ’what to do after you already have a good system’ mentioned by axo0oxa is a good point. And something I could add to.
Once I have a ’decent’ system, (2010) I left it for a number of years. Mainly I finally bought some high end interconnects. Then I started last year on the system again, starting with te best speakers I would ever buy. Going from 3.6 Magnepans to 20.7 Magnepan.
I wondered what to get next, but ended up buying a high end SACD player to use mainly as a DAC. (The usual thing to get, a new amplifier, my trusted dealer said I did not need one, So I accepted his advice..) I COULD have gone for a Rega P10 turntable. But my previous DAC was a used $250 device... And I thought I also own already a Kuzma Stabi/Stogi S turntable which is pretty good already
Then I suddenly got back to some basics. Power cords, a few, that instilled the ideal to finally buy some real better AC duplex. and actually that was because they were on sale, getting something that is considered on of the best possible, at half price,, I jumped on it! Even though I did not start out to do it.) Discovering how much a difference a few made, I went crazy and replaced the entire system wide duplex, including replacing the AC duplex in the two power conditioners.This also was a ’get the best I can’, since I will never re-visit buying different ones. I went back to a basic underlying thing. (like when I bought cables, so those would last through other changes.)
So I kind of would say there are TWO areas of a SYSTEM.. the main part of components, and the underlying structure, like cables, AC, cords, conditioning, even racks.
At this point I am resting.. Actually just adjusting (still) the little bits, like the resistors in the midrange of my speakers. After spending months critically listening and adjusting... I am tired of it, and just want to listen to music...
But in the future.. I can see revisiting the turntable upgrade, and by another year will need at minimum new cartridges for my two TTs.
So my upgrading went in two cycles, the components, and the support system of cables etc. Curious the components, I cannot really say I am finished, the support some parts I did go as far as one can go.