Speakers are the first piece of the puzzle

Jim, I have found after many years of attempting to get a system I could live with in my retirement, I had to make some changes. Much of this mindset was an undying curiosity regarding tube amplification. To find out, a speaker change was necessary. I sold my beautiful Dynaudio Contour 5.4's, and since buying anything new was out of the question, I opted to purchase, on Ebay UK, a pair of vintage Tannoy HPD 315 drivers w/crossovers. (This was a return to Tannoys, I had my first pair of 12" Monitor Golds in 1971, and due to a major lifestyle change, away went the Tannoys in 1988). 

I had a pair of 150 liter bass-reflex enclosures made, that was two layers of MDF laminated, for a net of 1 7/8', with a weight of 192 lbs. each. To my surprise, they have worked out well with either my SET 300B amp. or my kit-built Class D Audio (running two modules bridged for 500 Wpc) The Tannoys sound beautiful on either one. By this time I had already established a pretty good base of source components, making upgrades as necessary due to attrition (failure from age related issues).

So for me, it's been speakers first, to match speakers/amplifier, and then to upgrade source components as the need arises, until I've arrived at the destination that most pleases me. I have no desire to make any changes now, aside from those necessary from equipment failure.

It's an extremely comfortable place to be, listening causes absolutely no angst, just day after day of enjoyment. I hope everyone can reach this lofty goal.

Best regards,
Dan. . 

Speakers alter the sound more than any other component, maybe, unless we’re including analog sources. This should not be surprising, because the speakers must convert the electrical signals to sound waves through mechanical means. Thus, they distort the sound far more than any DAC, amplifier or CD transport.

Whether it’s prudent to buy a particular part of the chain before the others is endlessly debatable.

The OP has it right with the thread title.  The speakers' sensitivity spec and overall performance needs will inform your amplification.  If you're in the ultra high efficiency mode then you can be looking at SETs that have those few, but glorious watts necessary for your speakers.

In my case, with low efficiency speakers, I knew that a higher power SS or perhaps prohibitively expensive tube beasty was going to be in house.

After that it's an allocation of available $ as to the sources, line stage (if needed), cables power conditioning, footers, yada yada yada.  For me it's the yada stuff that's fun.  Eaking out that last bit of musicality by attention to the minute details of the system and room is where the fun is for me. (With the obvious exception of opening the box of new gear for the first time).  Hey...who out there doesn't love that new car smell?

Interesting topic as always. What came first, the chicken or the egg? Let me ask, when one becomes dissatisfied with the sound of their system, what do they change out first? Cables, amp, source, footers (giggle)? I'll bet speakers. Ultimately, that is where the sound (music) eminates from. It's the obvious choice. In many years of this wonderful and sometimes baffling hobby I have found all the links in the chain have an affect on the sound. Personally, I find the speakers have the final say. I've never had a source or amp (or cables) that I couldn't live with. I have had speakers that just didn't cut it (to my ears). Enjoy the ride...

Well, you have to start somewhere! First, you have to have a room. This seems obvious, but don’t laugh. Consider the size of the room, what other uses are going to be made of it, how much room do you have for audio stuff. For example, my all-time favorite loudspeaker for “realism” is the Magnepan. But that speaker has very demanding placement requirements and needs a lot of room. So, yeah, start with the speaker, considering how it’s going to work in your room, visually and aurally. And are your own speaker tastes a little idiosyncratic; I.e. are you “horny?” Then, think about the amplifier. How much power do you need to make your chosen speakers sing? If you’re a tuber, you should favor speakers closer to 90 dB @ 1 watt efficient and be aware that, as a rule, tube amps interact with conventional speakers idiosyncratically, so consider the speakers and amp as a package. With sources, your first question should be: which ones? Today, there are 3 choices: vinyl records, stored digital (including the shiny discs and downloads) and streaming audio. If you don’t own any existing media - or own digital only - I’d suggest a DAC, a network player/streamer and some sort of NAS (which, initially, can be your computer). There are also units that combine one or more of these functions, including a DAC/preamp which includes an analog input to allow for the possibility of getting into vinyl.
Or you just cut the BS and buy a pair of KEF LS50 “wireless” (you still have to plug ‘em in).  Add a streamer and some NAS and you’re good to go.