going speakers first, might lock a person into a particular camp and I see that as a sort of drawback.
if you grab a pr of panels because of how they image perhaps, then decide you want to try out an 8 watt 300b amp, it's speaker selling time!
Yes. But that is no different than buying an 8 watt amp and then deciding you want to buy Maggies. Now it's amp selling time! I think you were right when you said that everything matters. That's why it's amp selling time or speaker selling time - because the person was not forward thinking. If they were (and it's not always possible to be) then it would not matter what they bought first as long as they avoided things like big impedance mismatches.
Don't misread this, I certainly do not disagree one bit that the upstream components should be as good as you can get them. And yes, lower end speakers can sound great with higher end amps. But I think some lower end amps really do hit above their weight. Nait 5i, Exposure 2010s2, etc. These can be considered entry level but they definitely aren't bad. Same with their CD player counterparts. I guess your point would be if you go cheap on one part go cheap on the speakers and then try to upgrade those. Again, I'm not sure I'd disagree. Although, if you have resonance issues in a $500 speaker, that won't go away if you use a $20,000 front end. Nor will mismatches with the speaker and room. Surely if this is the case, a speaker change first is in order.
I guess I'm saying there aren't any hard and fast rules. You have to take each situation and evaluate it on it's own merits.