From Sonus Faber Extrema to...

It depends on what you think you are missing.  I own a pair of Vienna Acoustics Liszt speakers which I really like, but are always on the lookout for others.  I previously owned the Avalon Ascendents and the Liszt surpassed them, especially in the bass.  The Avalon customer service is bad.  I recently listened the the Wilson Audio new Sabrina.  My complaint with Wilson has been the upper end treble.  These are better but not to my taste.  I prefered the Liszt to the older version of the B&W 803's.  I use a tube pre amp and solid state mono block amps.  (Herron Audio).  Just my two cents.

Beautiful system. I agree that a CJ amp would be a big improvement.

I am a big Sonus Faber fan because of their relaxed, natural / musical nature. There really is not any other speaker like it, other that Serbin. I am very familiar with Wilson and B&W and they are very very different, as is Avalon than the Sonus Faber. 
 

If my understanding correct, that you want to sell yours and buy speakers with the money you get from them, that is an absolute no… you will be taking a big step down. If your going to add $5 - $10K to it then look at used Sonus Faber… Olympics .. Serefino… there are many. CJ or ARC are really great electronics paired with SF. 
 

you want to explore then you’re just gonna have to go listen to Wilson (fast highly detailed), B&W (rock speakers), and Avalon and see if they impress you. 

"They sound lovely paired with my Conrad Johnson MV125 or with the couple of Accuphase P360 amps I own, bridged to monos (actually I think the CJ is a far better match). "

Based on your own comments, you're just  showing signs of "audiophool upgrade for no good reason" syndrome.

Since there isn't at least a $15k fund for a nice used pair of SF's, why bother?

Reposition/room enhancements(if allowable)

Stay away from audio forums and listen to music is what I would do.

My impulse advice: Eggelstonworks Andra III.

Personally, I'm smitten by B&W 800 series D3 (I own 804D3). Best speakers for atmosphere, depth and detail I've ever heard (diamond tweeter?).

Always lusted for the Extremas. Always unaffordable (to me).

My ever faithful Revel Salon 2 speakers have been around for over a decade and a half, but I have no plans to replace them.  Why?  Because still I love the way they sound, even compared to todays more contemporary speaker offering.   The age of my speakers makes no difference to me.  It's all about how they sound.  There will always be something better or different out there to choose from.  But, at some point, you have to find speakers that you love, and just be content with them.  Recommendations and suggestions from others are always welcome.  However, as you well know, you're going to have to audition speakers until you find the ones that you love.  And, when everything is said and done, based on overall sound quality and your budget,  you just may discover that your current speakers are your best option after all  Happy listening.