Help with speaker selection

For extreme listen-ability (no harshness), but with more detail, I would suggest Rosso and Audiovector.

Like Sonus Faber, Rosso has a silk done tweeter, but it also incorporates a supertweeter, which I believe adds to the resolution, especially instrument decay. SF can sometimes feel slow to me, and Rosso isn’t as sluggish. Certaldo and Volterra are Rosso models around the price of the SF Nova line. Like you, I also like the bass thump from SF, and I believe Rosso keeps much of the bass weight but improves upon the bass definition.

I believe Audiovectors are resolution monsters with their folded ribbon tweeter. I’m not sure if they would fit your requirement of extreme listen-ability, as I think of them like a dry wine. They might appear bright, or neural, to you, which you may find to be off-putting, or just fine. They won’t be warm like SF.

When I went looking for my Livingroom speaker, I realized that coherence in the sound (with driver-based speakers) was amongst the top attributes I should seek.  The speakers I was demoing usually had drivers made out of different materials and sometimes that did not sound like one voice. I felt some discontinuity in the bottom range.

My worst audition (because of the room) was the speaker I ended up getting because the 3 drivers sounded like 1 voice. I did near-field listening, almost like headphones to demo the speaker. That speaker was the Yamaha NS5000. The drivers are made out of a material lighter and supposedly faster than the BE material used in the Revel Salon, Paradigm 9H, etc... The coherence part is likely because the tiny tweeter and the 12-inch woofer (plus midrange) are made from this new material, Zylon. 

Yamaha spent a lot of time and likely money researching the tech used in this speaker. They built their own drivers, used some exotic wood from Japan, and I think made a tremendous speaker. So much so that I threw out my shipping boxes. I will see a box before my NS5000 sees another box.

The NS5000 is the successor to the NS1000 from the 1970's. That speaker was the first to have both a BE tweeter and midrange in the same model. Today Paradigm touts that as a big breakthrough in their top end Persona line. Yamaha seems to have some serious audio research chops going back a while.

The dealer that I went to audition the Yamaha had it stuck in the worst possible room. They had the Sonus Faber in the best room. I could tell that the Yamaha did not have the prestige of the Sonus. I had no interest in listening to the Sonus because I found them dark. However, my understanding is that the latest models are not like that. I should have listened.

I'd ad Vandersteen Quatros CTs. They're in the 17k range I believe. Vandys are well known for their musicality and listenability but when they add carbon tweeters to a speaker the detail is amazing. They also have room tunable subwoofers built into each speaker to allow you to mitigate room modes some which really helps with bass definition. Take a listen somewhere 

Your JC1 is a musical amp. You do not need musical speakers like sonus Faber it will be too warm unless you bipass Olympics and go to the more hi fi and accurate Serafino.
in your budget I would look at about an 18-20k pair of Vivi Audio Kaya 45. They will open up better and have good synergy. They are also easier to drive and you won’t need JC1 just a JC5+ stereo amp.

If you stick with the JC1 Vandersteen Quattro will be also amazing with that amp. They are phase and time aligned and need a lot of power.

For resale another good speaker is the new 45k Wilson Audio Sasha-V but that might me over your budget. The smaller Wilson’s don’t have the bass.

I re read your OP. @hk_fan I also researched your implied speakers, and I agree with @mikekollar You should research the Legacy Audio Speaker line. Your JC1’s will drive them just fine, Suggest you consider the Focus XD with Wavelett II or if you want to go all out maybe the Aeris. The Wavelett II is the icing on the cake IMHO. This brand flies under the radar to most audiophiles but has many raving fans for those who try them. The attributes you are looking for in your post are up their alley. Revealing, dynamic, bass definition and slam. hey will fill your large space easily. They are made in the USA so the cost of importing from Italy for example is not included in their price, they are a bargain.