Sound quality impact - preamp vs power amp?

the whole point of high end audio is trying to eliminate the weakest link.

I disagree.  I believe the whole point is to optimize the synergy among your components & room to best connect you to the music and stir your soul.

If I didn't know better and only read some of these posts, I'd think all I had to do was get easy to drive speakers and piece things together from there. Good lord.

Everyone is missing the point here. How many excellent preamplifiers are in existence vs. excellent amplifiers? The point is that it is extremely difficult to find superb preamplifiers which will make your system sound better, and they are plenty of good to excellent amplifiers to be found. That’s why my vote goes for the preamplifier.

Depends on what future plans are. If you put more into one than the other do you plan to upgrade the lesser soon. If this is going to be more long term setup i would say get an amp and pre-amp that match well. If you get one higher quality than the other then you will not get the most of the higher end component.

I don’t know.

What are your current  sources?

Is the preamp/amp solution your last upgrade?

I have upgraded my system in stages and each step was a noticeable improvement. 
I did the upgrades based on a goal and took advantage of sale items of demo equipment. 
I upgraded from a purely analog system in several stages:
1.  Bluesound Node 2i. Adding digital streaming to a purely analog system. 2.  Added a preamp with a phono stage and DAC and used my integrated amp as an amplifier. 3.  Then I bought a stand alone amp
4.  Then I bought a new standalone DAC. 5. Then I upgraded the speakers 
6. Then I upgraded the turntable 

if I did it all at once - I would consider an integrated amp. There are many good ones available. 
I don’t know if you listen to vinyl, CDs, streaming or a combination of sources. 
Trust your ears and determine if your system is a journey or destination.  And good luck