Responses from rick_n

Front or Back wall diffusers
You have a very nice system.  If you diffuse the front wall between the speakers they will image even better which is really saying something.  The idea of diffusion is to scatter the signal so the reflected sound doesn't return to the listener as... 
Best EXTERNAL DAC suggestions
Might want to check this....but if you're using the Node as a Pre then the output is an analogue signal.  Not sure how you work an external DAC into this configuration.  
I Hate Moving
Don't forget to label your cables before taking down the system.  
Distance from wall for KEF Reference 1s
Every room is different so you will have to spend some time trying different positions to see what your ears like.  What you "hear" is the only thing that matters.  I have KEF ref floorstanders in my TV room but that is for an Atmos setup so recom... 
Subs with room correction DSP?
My short answer:  I have two SVSs in my HT room and a single JL Audio Fathom 112v2 in my two channel room and they are both excellent in their application. I'm very pleased with the results of the JL room correction.  The JL sounds very fast, smoo... 
Inexpensive streaming amplifier
My young daughter just moved into an apt too.  She went with an "open box" Powernode ($750 with factory warranty) to drive her KEF LS50s.  She's VERY happy with her setup.   Since it's for a girl, go with an all in one solution, smaller footprint... 
So many YouTube clips to evaluate sound quality. Why???
YouTube vid to show off SQ....what a joke and waste of time.    
Moving on a sailboat - bookshelf speakers?
Congrats on the Sailing trip, safe travels.  There are lots of choices that are front ported designs.  I would stay away from anything rear ported since it will need more space.  
Best Amplifier & Speakers combo?
I would offer two suggestions.  1-Take the LS50 over the Q series, noticeable bump up in SQ IMO.  Both of my kids bought used LS50s and are very pleased. 2-The non-Meta KEF R3s are being discounted now and should be a strong consideration.  They w... 
I'd like to help but I'm confused.  OP is asking for a help pairing a sub to a two channel listening system but lists both KEF R3 AND KEF LS50 as the speakers.  I'm confused.     
Poll: Most impactful component
Speakers then DAC if streaming  
How To Keep Cat Off Stereo Equipment?
Cats are like children....easily distracted.   Get a cage full of mice and keep the mice in another room....case solved.  ;D  
Are carbon fiber speaker cabinets inherently better than wood or metal ones
How many violins or highly regarded guitars are made out of carbon fiber?  Pianos?  Just wondering.  
Bang for the buck
I like your idea of the KEF R3s.  If the KEF sound is to your taste they are less picky about placement than many other brands. This is helpful in a smaller room where there are limited placement options.  Down the road you will want to upgrade th... 
What is the most challenging music to play on a stereo?
For me, busy rock music with piano.  Large bands with many instruments competing for space are challenging to record and mix and then reproduce.  If this can be resolved then I'm always impressed.