I should start with speakers. This I know. I’d like to establish a new system.

Returning to a hobby I abandoned two decades ago as life interfered with my personal desires.

I am currently drifting between horns or BBC sound. Two different worlds, but each intrigue me. Considering Volti Audio with Cary SLI80 Integrated while also Harbeth 40.2 with something like a VTL MB185 Series III. Schizophrenic I know.

Dedicated Room 12’W x 30’L x varied vaulted 11’H.

Your room is long enough where you can set up 1 pair of speakers on front wall and another pair of speakers on the backwall.

Rotate the chair 180 degrees everytime the schizophrenic hits.

Personally, I would ignore the BBC stuff and go with a) a horn and b) a panel llike a magnepan or something.

@yyzsantabarbara  KEF Blade Meta? In a 20k budget? Is that possible?

food for thought https://speakerchoices.com/

Acoustic treatment.

The room will dictate at least 50% of what your system will sound like.

@tomcarr  Agreed. 

If I was in the position of the OP, I do the following:

1. Try to size up the assets and challenges of the acoustics of the room. 
I'd lay hands on whatever gear I can find to listen with.
I'd listen, position, and once some reasonable positioning is established, I'd measure for frequency response. 

2. With the information gained above, I'd try to treat the rooms major flaws, focusing first on 20hz to 300 hz, since those frequencies have to be mastered before dealing with the rest of the range. I'd work a bit, next, on 300hz-20khz.

3. Having brought the room to a baseline of decent response, I'd do a bit of research on speakers and amps that will match my tastes and my room. 

4. Next, I'd start borrowing speakers or buying, used. I'd get a decent solid state amp (used, hopefully a keeper) that can drive a bunch of speakers. 

That would be the "launch sequence" to getting the basis of a good system going, in my opinion. 

Sum:

• Get the room ready.
• Try speakers and amp.
• Get final speakers.
• Get final amp.
• Figure out how to optimize the rest (preamp, DAC, cables, power, additional treatments, subs).