System assessment...

As a retired person learning about streaming music will make one’s life easier. I’m pretty sure they invented it for old folks. 

Maybe it’s your room. You never mentioned if it was treated or not. Do you have tiled/wood floors? Windows? These things would make your room more sterile sounding. 

Congrats on retirement, I am three years in and enjoying it very much. And a nice system, I too have the Reference One’s, a very capable speaker. How is your listening time split between analog and digital? Any plans to add streaming?

If you are leaning towards digital, then a separate DAC is a consideration. Unfortunately the Mimas does not have a preamp input which would allow you to experiment with some different preamps. I have been on a preamp quest for the last several years, and it is certainly a large part of determining the sound of your system. I recently upgraded from my Pass preamp to Audionet, this has been quite a revelation.

Not sure what central Wisconsin means, but I am in Duluth if you want to hear a different front end with the KEF’s. You are welcome to visit.

Congratulations on retirement! I’m in the same situation as you, and have been upgrading after many years of stasis in my system. I addressed high end hardness with replacing speakers and my preamp. Building upon excellent advice here, I have learned the most from attending multi day audio shows EVERY DAY (make a mini vacation of it!). Going every day reduces the anxiety of rushing room to room, and allows for more serendipity and reduces audio fatigue. My earlier experience in this method allowed me to zero in on speakers that sounded naturally extended in the highs but did not have a hot and hard high end. They ended up being a new version of speakers that I already owned. 
I especially agree with the comments regarding streaming. My musical horizons have expanded enormously through streaming, as it is so easy to explore. How else would I have learned about such wonderful bands as The String Cheese Incident or learned about the Grateful Dead’s Betty Boards?
 

Back in the day, I did run a tube pre and SS amp, I agree, likely the best balance of musicality.

Thanks to all. I believe my take away here is to get out of the house and visit Minneapolis and or Chicago. Recommendions for reputable shops?